JP tends to have players that are more respectful and a higher base skill level so it's not as big of an issue by default.
Not sure if it's the case nowadays, but years ago at least, I had heard/experienced in lower dungeons at least, that wall to wall pulls were less common. This would be pulling likely 7/8 (strong) or 9+ adds at a time between bosses, only stopping when the game doesn't physically let you gather more adds. The issue is that this playstyle is only possible under minimum skill requirements. You need a tank that is capable of rotating mitigation properly, you need a healer that knows their kit well enough to handle the damage in stress, and the damage output to kill the adds before the tank and healer run out of resources since mana and defensive cooldowns are a limited resource. If any of those are missing, you will wipe.
What will often happen is, people (other than the tanks, more commonly dps's, but sometimes healers) will force this situation in every dungeon, regardless of the content level, regardless of their experience with the other players in the group and can possibly wipe the team for no reason. When you have a higher population of "new or low skill" players, this becomes a problem. While this method is expected in high end content, that learning process/curve, imo, is to be handled/discussed by the tank and or healer for what they are comfortable with. As a healer, I will give confidence to my tanks. As a tank, I will give confidence to/advice to my healers if they're open. But there are times where people have anxiety, where people have lag, where people have irl distractions, where that expectation is not going to be met. And instead of discussing that beforehand, it'll be a dps not caring about those factors forcing the situation and causing people's gear to break and the run to take longer because they cause wipes or throw off mitigation rotating.
When you run into enough of these people not being considerate of others, it spawns the mindstate from those of us who can handle bigger pulls, to start punishing people who actively disregard the situation of others in an effort to dissuade them from doing it with random people. Depending on the details of how the aggro is taken by the person pushing the party to handle more and what gets said in chat, you may not have a direct violation of ToS that is easy to report, and it much easier to just enforce YPYT and cause that rushing player to die repeatedly than to deal with filing a ticket. After they die once or twice, they will fall in line after realizing that they are now the one's making the run take longer because their dps is gone and time to group adds is still going to be the same.