Well firstly, these two best friends were wholesome and adorable and I wish more had a relationship like this. Straight up BFFS.
And really, the princes kinda resembled their friends, so that they'd be attracted in this way isn't strange and also cute in its own way.
....At the same time, this completely took all agency from the ladies and out in public was not the time or place to spring this on them. Kind of a dick move, and if the girls weren't into it, the tone would've turned out quite differently.
That said, it might be a matter of limited time and wanting to fit the villainess plot structure If the author to this one gave it a fair shake and elaborated the full romantic journey, I'd be all over it.