As someone whos bellow avarage in terms of height I kinda get him. It hurts enuff people keep plastering to rise one's height "just play basketball etc" while never once thought genetics play a good chunk of part for it. Mustve been hurt to hear that hopeful feeling only to realize shes just teasing to see ones reaction.
Honestly, if we were to stop and look at this story seriously for a moment, and not just consider it a dumb romcom, what she's doing to him is actually extremely cruel and possibly even traumatizing. He's not just short, he's super short and he's going to go through his whole life facing prejudice and discrimination (because of stereotypes about masculinity, etc.) because of it, and he already knows it. She's constantly coming up with new and insidious ways of reminding him about it, even doing shit like this where she raises his expectations only to crush them again. Since it's a romcom, it's supposed to be cute, so he just takes it in stride and falls in love with her like he's supposed to, but if this was real, it wouldn't be strange at all if he started hating her guts. She then justifies it to herself by saying that "even if society judges you for it, I think your height is fine", but like, bitch, your opinion is not the only thing that matters. His entire life isn't going to revolve around you, even if you do end up getting married. He's still gonna have to function while interacting with the world outside of your relationship, where he is going to be judged and treated differently, and he's going to need strength and confidence to do that, not have his loved ones constantly bully him about it.
I'd really like to see an arc where she actually goes too far and she has to face the consequences of her actions and reflect on them, but I guess that probably won't happen, given the tone of this manga so far.
That's one thing I really like about Nagatoro. While it starts out pretty similar to this (or even worse, arguably), Nagatoro gradually softens and becomes nicer as the story progresses and there are even scenes later on where she explicitly apologizes to the MC about how she treated him early in their relationship. That makes it a lot easier to accept and root for them as a couple, instead of this where it feels like the author doesn't even consider what Oohara is doing as problematic.