I’m taking this as meaning Eric is indeed present day Neverland rather than flashbacks which means Eric could totally be Regina’s new love interest. Maybe Eric tries to pursue Regina romantically, but she sort of rejects him for various reasons (focussing on finding Henry, lack of self-confidence, etc) then when she is ready to open her heart to love, she finds out that Eric has moved on and has fallen in love with Ariel who loves him back. That would be tragic for Regina.
Well it makes me wonder how close the set are. They must have a few: SB set, NL set, FTL set, not to mention the outdoor sets they still use to a lesser degree. It’s possible that he just stopped by to visit and say hello without him actually being in NL.