I (& pretty much everyone else, except for the delusional fanboys) came to that conclusion when his rinnegan was closed after their encounter with Madara (but you're overlooking that), and the fact that he said his eye was ready this chapter. If he only used Amatersu, then you might have merit. Sasuke has spammed Amatersu before with no noticeable signs of prep, heck he (again) did it this chapter in the ice. You're telling me a MS ninjutsu requires more build up than a rinnegan tech? I guess he has some type of infinite chakra pool now? Yeah, If Sasuke's teleportation was that drop of a dime convenient he would have teleported him and Naruto out of the ice, or better yet teleported away from Kaguya's clutches before she dimension dumped him. Bottomline his teleportation drains him thus requiring his eye to rest a bit.