Six paths Naruto was not a temporary powerup. Naruto still uses RSM to this day. He even proved that he still has the bijuu chakaras when he threw a lava rasenshuriken at Delta. He also proved this in the most recent anime episode by talking to the bijuus in the meeting place.
Having all Bijuu chakra is just the first step to awaken Six Path Senjutsu(SPS) chakra. Second step is to combine all them together into one and you need special "tool" that's Gedo Mazo. Without GM you couldn't get complete Six Path senjutsu chakra without being Hagoromo. The rule never change.
Another rule,
To have Senjutsu chakra you need to learn how to get it. You can't inherit this kind of chakra. Same with Six Path senjutsu chakra. But there's still a level of difference in the whole process. Ok let see this, if having Six Path chakra+the ability to mold senjutsu chakra are the requirements to unlock SPS chakra why Adult Naruto still doesn't have TSB? If having all 9 Bijuu chakra+Six Path chakra are the requirements to unlock SPS chakra why Adult Naruto still doesn't have TSB or why Sasuke's lightning Susanoo didn't get TSB orbs? If having 9 Bijuu chakra+Six Path chakra+Senjutsu chakra are the requirements to unlock SPS chakra why Adult Naruto doesn't have TSB and ability to fly? Can you answer these without using headcanon?
Showing to used Lava Rasenshuriken doesn't mean Naruto possesses pure SPS chakra. It just mean that Naruto can used other Bijuu technique. Being a meeting place is not part of requirement. You need to combine all the chakra into one and get the special ingredient inside GM to produce SPS chakra. There's no other way around.
So here what can I agree is that Naruto possesses a form of Six Path chakra but not 100% complete. And Not to mention that SPC is Rinnegan chakra. So how could someone who not possessed Rinnegan could have SPC?
And you also need to remember that Naruto never awakened SPS chakra naturally. Hagoromo have gifted Naruto with his Senjutsu chakra and Rinnegan to Sasuke. Senjutsu chakra can be channelled into other people as shown by Juugo to Sasuke but it just a temporary power up for the receiver. It also applies to Hagoromo gift(SPS chakra+Sun mark) to Naruto too.
So yeah, It just a temporary power up for Naruto.