The only timing distinction that does matter is whether you apply the Maps or SN first, and that will only determine whether SN returns to the island face down and remains face down, or if it returns and then immediately gets flipped face up.
Maps of Alexandria says “turn all treasure on all wild islands face up for the remainder of the game”, so wouldn’t SN go face up regardless of which is applied first? “For the remainder” seems like it applies to any and all treasure put back on wild islands at any point in the future.
SN’s loading restriction only applies to optional treasures, like standard coins and UTs that would normally load face down. You still have to deal with any and all other UTs normally.
Good to know – for some reason I didn’t read the Code entry for it yesterday since I was mostly referring to the Explore Action order of operations. I’m glad it’s already addressed in the Code, but it does feel like an odd exception to the “abilities taking precedence over rules” thing, since faceup UT’s must still be loaded despite the ability text of the UT implying otherwise.