It isn’t, it’s a combination of all nature types and yin-yang release. It literally nullifies everything.
I forgot about the convo too actually. Anyway, I'm aware that the truth seeking balls incorporate yin yang release and nullify ninjutsu, however even yin and yang release are still chakara natures (with emphasis on the word chakara). Therefore something that absorbs chakara like a karma seal or preta path could possibly still absorb a truth seeking ball.
Now note that I said possibly. I am not guaranteeing it. However, like I was about to say before, we have never seen anyone actually try to absorb truth seeking balls.
Before you repeat the statement that truth seeking balls nullify everything, just remember that technically even that got disproven by the manga since the balls don't nullify senjutsu. The balls also don't nullify extremely advanced taijutsu such as Guy's techniques. Having said that, the balls aren't as infallible as they were first presented to be, so it is possible that another weakness to the balls can be found in the form of chakara absorbing techniques (which I reiterate that we have never seen be used against truth seeking balls).
Honestly, the debate of truth seeking balls vs chakara absorption techniques like preta path is a very similar concept to the whole unstoppable sword vs unbreakable shield paradox. You can't have both a sword that can cut anything and a shield that endures anything because if the two clash, then that will put an end to the claim to fame of one of the two objects. If the shield endures the sword's strike then it has been disproven that the sword cuts through anything. Alternatively, if the sword cuts through the shield then it has been disproven that the shield endures anything.
In the same way, when you take a technique that is supposed to absorb anything and put it against something that is supposed to nullify anything, one of them has got to give.
Anyway, as far as juubi Obito goes, I didn't factor in the rinnegan because Obito practically treated the eye like a contact lense (something which annoyed me greatly).
Don't misunderstand, I am not like those guys who say that Obito couldn't use the rinnegan. No. It's just that he hardly did use it, and he didn't even bother to use it at all when he was the juubi's jinchuuriki.
Also, about the spacetime techniques creating an opening for Obito, that is only assuming that Jigen uses the portals in the way that you are thinking he would. He could potentially just simply throw the portal on to Obito in the same way he did Naruto and just warp Obito to that dimension and leave him there (and without kamui, Obito can't get back). Even if not Obito, Jigen could warp away the truth seeking balls and effectively rob Obito of the balls in the same way that Minato did to Madara.
Now there are some points that I will concede to you:
Obito did possess much more fire power than what we have seen from Jigen thus far.
I'll admit that I wasn't thinking as much about fire power when I said what I said, as I was thinking more so about the practicality of Jigen still being able to traverse dimensions (while Obito for whatever reason could not use kamui as the juubi jinchuuriki) while also being able to fly and absorb chakara amongst other things. There is also the release function of the karma seal and likely plenty of things that we don't know about.
However, the main reason why I didn't really want to rank Jigen right now in the first place is because I doubt that we have seen everything that he (and more importantly Isshiki Otsutsuki) can do.
Anyway, for now I will recant my statement of putting Jigen above Obito, but I'm not quite going to put Obito above Jigen yet either. I really just want to let things play out more and see the power of Isshiki Otsutsuki.