Nah, I don't think the creators went Bella/Edward Twilight. ; Oh the Gods. Felt canonically underlined that it was being used specifically as a healing act; given its "in the face" narration to make sure the kids had no empty spaces to misinterpret or feel confused about, immortality probably even would've been mentioned during, "and she ruled the kingdom with the same wisdom as her parents." (or etc) Rapunzel very much ages like a normal person (infancy - young adulthood). Anything filling gaps not already filled in that movie is just that.
In regards to Frozen, Disney has done many "Finding Waldo" character inserts in other unrelated Disney movies for years. Notice how Rapunzel/Eugene are nowhere in any of the crowds afterwards, most notably the chapel when the entire audience is laid before the screen, and also where they would've been front-row due to the connections fans theorize between she and Elsa/Anna.