It could be a gamerule, just like dismemberment, i.e. it can be turned off or you can set a threshold for it. There's no reason why it would on by a default for all the existing mods, especially considering the fact that it changes the gameplay and probably wouldn't be compatible with older clients.
Sometimes when you grab someone and pull too hard, your wrist breaks off. A new thing you could try is to set the ungrab threshold the same as the dismemberment threshold, so you're more likely to just let go instead of your wrist breaking off.
One of the changes to the serverlist is to grey out the rooms which you can't join. So if there's a room using a gamerule which your client doesn't support, you'd hope to see a message saying something like "you need version 4.x to join this room"
There are a lot of users who don't update toribash. There is no intention to make changes which will break the older versions of toribash. Especially if it changes gameplay.