selective narrative is at work again, since BZ's statements are clearly followed by a question mark and not a period. Therefore, it's him inquiring to himself about it. The fact is, if Sasuke was immune to it then he could afford to be outside that Susano'o. More to the point, it would defeat the purpose of Hagoromo telling the both of them that everybody were prone to being a victim, and that statement very much included the 2 of them.
it doesn't matter whose speculation is more important than whose, since BZ don't know for absolute certainty; hence the question mark :eww:
Hagoromo didn't say Sasuke was immune, and he said EVERYBODY stood to be a victim. He didn't point out either one of them being immune just because they were being given new powers, hence the whole point of him telling them that they needed to stop Madara before he could use the genjutsu. Sasuke pretty much pointed out that it was the Susano'o keeping them from being under it already. No one said anything of the sort that his Rinnegan was why. Even if he was, what was it going to change? He sure as hell wasn't going to be able to solo multiple Shadow Madaras.