This specific scenario is one I see all over the place in Korean and Chinese manhua. Usually it gets on my nerves, but I don't really mind it here.
It always feels so petty. Especially when they're so desperate to make it sound like the MC is so above this that he doesn't care what anyone things of him.
Yeah, he doesn't care at all what anyone thinks of him, because they don't matter. He just happened to come to a gathering of old schoolmates/relatives who used to pick on him, and just happened to insult them every time he opens his mouth, and just happened to use the first chance he gets to throw around his wealth and connections to in a flashy display. These are clearly the actions of someone who doesn't care what people think of them. Of course, they'll also be sure to remind you every other sentence how little they care what people think, in case you forgot that they don't care.
But here? It works. It super works because Grid is a petty, vindictive, insecure, greedy piece of shit by design, and we love him for it. He's a lovable asshole, but he's still an asshole. It makes sense that he would pull some petty shit like this, and I think it's super refreshing to get a manhua MC with an actual personality. Admittedly, most of my manhua consumption is xianxia, so it's very possible that's unfairly painting my perception. It might also be hasty to lump Korean and Chinese media under one umbrella, but the trope similarities are hard to ignore.