I'll give it one last go. I'm sure you can understand. If not, tell me where I lost you.
1. Fanservice isn't inherently sexual. Let's make sure we understand this first. If a character in Smash Bros. has a move or taunt that's a reference to their prior games, that is fanservice. For instance, the way Megaman moves in Smash is fanservice.
2. Giving Samus an outfit that she wears as a sexy fanservice reward for completing the GBA games under certain constraints is both fanservice, and 'sexy' fanservice. It's a nod to an earlier game where it was sexy fanservice there, also.