I have played this game so many times and have tried to look at all the stuff contributing to strong vs weak hits, along with that I do boxing and karate. Done tournaments for kickboxing so I know what is a hard punch based on technique, half the people on the game can knock you out even if you have good footwork and defence. But when you want to use proper technique with all strength the hit counts as weak, the annoying part is the training is super mis leading to. So when I try these techniques on the dummy they say decently powerful hits, in online they are weak.
Further more if someone gets tired because they were spamming, so now its your time to attack they'll hug you and get no punishment for doing over and over again until they recover. I really hope the devs punish this behaviour in the future and make the damage weaker on wild haymakers.