That image that you claim that I put out of context speaks for itself. It is Kaguya herself remembering being sealed by a young Hagoromo and Hamura.
Just to make sure that we are both talking about the same image (because I honestly think that you are referring to a different image from the one that I am referencing), I am talking about this image:
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Now,
can you honestly sit there and tell me that Hagoromo and Hamura are not using rikudou chibaku tensei in the above image (especially considering that we see Naruto and Sasuke doing the exact same thing in the lower image, and we know for sure that this was when Naruto and Sasuke sealed Kaguya away)?
Also, primary and secondary sources do matter. You acting as if it doesn't matter on the grounds that "all of it is information from the manga" is like insinuating that a character can never be wrong (even when we know that canonically in universe, said character was deceived or manipulated). I get that characters speak for the author, but at the same time, there are times where a character is revealed to have been misled, deceived, to have misunderstood, etc... We have seen so many instances of this in the Naruto manga.
Examples:
Itachi was convinced that Madara stole Izuna's eyes and that Madara was the one who attacked Konoha with Kurama and helped out with the Uchiha massacre. He told all of this information to Sasuke, and to us the readers. This was "information from the manga" as you put it. Yet, we later find out that Itachi was simply wrong. Madara did not steal Izuna's eyes. Izuna willingly gave his eyes to Madara as he was about to die. Also, it was Obito, not Madara, who attacked Konoha with Kurama and who helped out with the Uchiha clan massacre. Itachi (along with most people) was simply deceived by Obito.
Going even further back in the series, Kakashi once said that the sharingan was derived from the byakugan. Was that not "information from the manga" as well? Yet, we came to learn that this is not correct. Yes, both dojutsu have origins with the Otsutsuki clan, but the sharingan did not derive from the byakugan. It was a dilution of Kaguya's rinnesharingan which she awakened as a result of eating the chakara fruit.
Even Hagoromo himself has been proven to be wrong on occasion or unaware of something, as he was not even aware that Kaguya was the juubi. He believed that the juubi was the divine tree that was fighting to reclaim its fruit.
So yeah... It definitely matters whether the character is a primary or secondary source, or whether or not that character was manipulated/deceived by someone, or whether there is just something that the character doesn't know, etc...
Anyway, let me show you how the timeline of events for Obito's explanation and the timeline of events for Black Zetsu's explanation contradict each other:
According to Obito, Hagoromo fought the juubi, sealed it inside of himself, and then on his death bed he split the juubi's chakara into the 9 bijuus and sealed the mazou into the moon. Now keep in mind that the sealing into the moon was supposed to happen on his death bed (when Hagoromo would have been very old and wrinkly like in the following image):
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Now, let's start from the creation of Black Zetsu. We know that Black Zetsu was created before Indra and Asura were born (or at the very least long before Hagoromo was an elderly man on his death bed) because of this sequence of scans:
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Black Zetsu says that Kaguya was sealed by her children, but just before the seal took hold, Kaguya created him (Black Zetsu).
Then, in the next scan, it says that Hagoromo neither knew that the juubi was actually Kaguya, nor did he know that Black Zetsu was secretly working to restore Kaguya.
Then in the third scan, it says "around then, ignorant of all this, Hagoromo was raising Indra and Asura" (as the picture shows a young Hagoromo, not an elderly Hagoromo, and a young Indra and Asura).
Now, let's focus on this line: "around then, ignorant of all this, Hagoromo was raising Indra and Asura"
The "all this" that Black Zetsu referred to was the fact that the juubi was Kaguya and that Black Zetsu was working to restore Kaguya (as stated in the previous scan). Now, it says that Hagoromo was raising Indra and Asura while being ignorant of "all this".
This directly implies that Black Zetsu had already existed and was already working to restore Kaguya when Hagoromo was raising Indra and Asura (or in other words, when Hagoromo was still young and not an elderly man on his death bed).
So... Now we know that Black Zetsu existed when Hagoromo was still young. Now let us recall when exactly Black Zetsu came into existence.
He came into existence just as Kaguya was sealed. This means that Kaguya was sealed when Hagoromo was still young.
Now, in what way was Kaguya sealed?
Well, this panel right here clearly indicates that Kaguya was sealed using the yin and yang seals - that is to say rikudou chibaku tensei
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What can we conclude from this:
We can conclude that rikudou chibaku tensei was employed when Hagoromo was still a young man. And of course, this scan directly shows this:
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Now, what does rikudou chibaku tensei do? Does it create moons or does it create jinchuuriki?
It creates moons.
The usage of rikudou chibaku tensei when Hagoromo was still young is a direct contradiction to Obito's notion that Hagoromo was old and on his death bed when the moon was created.
As one final note, I have a question for you:
If you still do not put any stock into the above scan, then please tell me what you think Hamura's role in sealing Kaguya actually was. I ask this because Madara and Obito have already shown that the process for sealing the juubi within oneself does not require two people, nor does it require the yin and yang seal. Six paths ten tails coffin seal only requires a rinnegan and a simple hand seal.