The “love at first sight” love is Eros or at least the beginning of it. Of course you can have instant sexual attraction and euphoria, certainly that can be a part of true love, but just because you have instant sexual attraction for someone doesn’t automatically mean it will turn into love. So I don’t think we should believe in “insta love.” Real love also involves friendship love and self-dying devotion love, and those don’t come instantly and those loves involve choosing.
Also, I think failure to realize the instant feelings for what they are can cause people to leave a relationship they previously committed to (“but I fell in love with this other person,” no you fell in lust) or commit to a new relationship before they really know the person.
I think this is why it is hard to find good love at first sight stories, most authors confuse attraction at first sight with love at first sight and so the stories end up quite silly. But the good authors take that instant attraction and deepen it with the story (or they may poke fun at it, or both; there are a couple versions of “insta love” in L.M. Montgomery’s A Tangled Web, some of which show how much wrong or hurt this thinking can cause or how a deeper relationship can develop, e.g. Peter and Donna, one of my fav couples.).