Board Thread:Episode Discussions/@comment-25319479-20170105115458/@comment-734582-20170109142431

Kakashisologod wrote: Hagoromo helped him awaken rinnegan faster, he didnt really gift him rinnegan. It seems that Rinnegan is a sacrificial upgrade with regards to the mangekyou. Sasuke is the only exception, and he's the only one we know got it directly from Hagoromo.

So Hagoromo did gift Sasuke his particular Rinnegan. Unlike Kakashi (who has no genetic potential for MS and thus didn't get it permanently), Sasuke has the genetic potential for Rinnegan. So once awakened, of course it would stay. There are no contradictions here.

besides, it's clear that Hagoromo gifted both chakra and powers, whereas only powers stayed. (as per the two known rules: chakra gifts are temporary, spirit-gifted powers are temporary unless genetic potential exists. See: kakashi, Sasuke, Tsunade).