Maybe it has some truth to that but I remember watching alot of sad stories yk those write a secret and leave a secret and one of them said "the only time my father says I love you is when he's drunk" and like when someone is drunk they might show their true personality but I don't think it's scientifically proven yet.
Another theory is that remember when Dan was asleep on the table with his hand bleeding? Jaekyung was staring for a bit too long and clearly it means that he cared even for a bit? But then he shook those thoughts away because Jaekyung believes that having positive feelings makes you weak

also this basically tells us that him being angry and grumpy is a conscious decision and not an innate/impulse reaction lol otherwise he would've also been like that when drunk
or is this another wack mingwa is writing