Sanji describes his time on Momorio Island as "hell". Despite what he lets his crewmates believe it has nothing to do with the lack of ladies. He spent two years either fleeing or fighting. He did not come away unscarred and did not have a fun adventure. An attempt at a canon compliant explanation for Sanji's reactions without just being a prejudiced jerk. Lots of trauma and internal narrative.

Waking up two years before their adventure even began was a surprise. The Straw Hats have to find each other again and make their way back to the New World and their dreams. Dealing with younger, weaker bodies and the weight of future knowledge they will find it's not as easy as a simple do-over. Every change has an effect on themselves and on the world. This story will quickly diverge from cannon. It will mix up, move around and ignore entire arcs. These guys are not looking for a boring adventure when they already have answers. What's the point in doing it all the same?

“Two boys can have sex, too?” Luffy grins as he says it, like this is a normal conversation. “No,” Sanji hisses vehemently at the same time that Zoro says “Yup,” grinning at Sanji with way too much teeth and seriously--who smiles like that? Luffy laughs and slaps a hand down on one of Zoro’s shoulders, leaning in. “Hey! Let’s have sex, then!”