With naturalRegen off, Hot Springs still Regenerate health, they should be disabled with Natural Regen off. This can be easily disabled in the config, but it should be disabled by default

Instead of completely disabling them, just turn off the regeneration effect? Perhaps bring back food regeneration?

Yeah, then others will say "Oh no, it should be ENABLED by default". Frankly, if you want it off, disable it in the config.

And this is why I didn't want you to make this issue, Clank :P

I wasn't going to suggest hot springs to be disabled, I'd simply suggest the water not giving a regeneration effect when the naturalRegeneration gamerule is set to false. The regeneration effect of hot springs is pretty natural if you ask me. We found it to pretty much break the game when you forget to disable it.