I think you have maybe misread the comment. Lihaun is not acting on his own accord, but following orders/guidance from the fujoshi character. She has already decided Yuyang is an "uke" and is tailoring her guidance as to what she thinks an "uke" wants. It doesn't matter what sexual position they have, presenting a big gesture out of the blue like the roses was inappropriate and not authentic.
It's obvious that he has limited social skills, but such a gesture backfired with the sign, it backfired with the clapping, it backfired with the bag full of drinks and it will presumably backfire with the roses too. Lihaun isn't reading the situation, and understanding the impact of his behaviour on Yuyang (or the context of where they are). The fujoshi character seems to have told him to act like a possessive partner "Don't look or talk to anyone else but me" also, which comes off as rather creepy, but these are likely common themes in the BL she reads. How long the author is going to draw this aspect of the plot out who knows, but the only progress should logically come from when Lihaun ditches his fujoshi fairy godmother, and speaks honestly, even if he stumbles.

I am not hating on anyone, however, I doubt a true fujoshi would have a potential seme treating his potential uke like a girl with flowers and whatnot. Yuyang is a man's man. Maaan