was it ever explained why adult naruto's spm changed?

[Hag0r0m0 0tsutsuki]

Rsm doesn’t change, neither in appearance nor ability. Rsm uses rikudo senjutsu, which has hallmarks that have remained consistent. When you see Naruto using rikudo senjutsu, and you’ll know when, that is how you determine when he’s in rsm. If he’s isn’t using rikudo senjutsu, he’d be using a Kurama Mode variant.

 

[Blackzoro]

The latest episode proves he can’t call on the bijuu for chakra. He didn’t even know if bee was alive. Meaning he used up all his chakra in his battle against Sasuke. That battle was after Hagoromo’s statement on Naruto being the meeting place.

Naruto could have went to the meeting place to see if we was alive but didn’t because he no longer had that option.

Did he try to call on the Bijuus? No.During Gaara and Shukaku’s conversation Shukaku stated he still had a connection with Naruto and the other tailed beasts but his connection with 8 tails was suddenly cut off (I’m guessing when Momoshiki attacked Bee) if 8 tails link was cut off then how would Naruto know if Bee is alive or not.

 

[Koibito]

It’s still RSM but without all the tail beast chakra and jutsu. Without 9 tome cloak and TSB.

Unless you think he doesn’t have anymore Of Hagoromo’s chakra

This is the best explanation I've seen as of yet, its simple, its still RSM using hagaromos half of chakra but without the usage of the bijuu chakra save for Kurama, hence the lack of pigmentation while also explaining the missing Truth seeking orbs which seem to appear in hosts of juubi or all 9 bijuu.

 

[gerizzyYMcrew]

The latest episode proves he can’t call on the bijuu for chakra. He didn’t even know if bee was alive. Meaning he used up all his chakra in his battle against Sasuke. That battle was after Hagoromo’s statement on Naruto being the meeting place.

Naruto could have went to the meeting place to see if we was alive but didn’t because he no longer had that option.

wrong again dumbass...and naruto helped break infinite tsukuyomi...so how about you learn to read now yes?

 

[Kadmos1]

Also, in the years between ch. 700 and the start of Boruto, all those years of peace meant there was not really a demand for combat training.