So it seems when you try to join a world on 1.21.131 while you're on 1.21.130 or lower... if the packs that exists on the world also require 131 then it simply disconnects with the error "Rabbit" (Failed to load resource packs). Hopefully this gets changed though I'm not sure how much they care about their disconnect messages.
It should return that the user is using a pack on a newer version than what the player is currently using. Whether that's possible or not, it would be nice to see more helpful messages like this instead of telling me to try taking packs off as a fix on their website.
This is only an issue when the min_engine_version is set higher than the users game version. It's useful to tell people that the game requires the latest version of the game to join your server but when it just tells me: "Search 'Rabbit' on help.minecraft.net for more information", I'd rather have a little better information since the fixes are normally unrelated.