gamerule naturalRegeneration not working

I think that this is probably a shapshot bug.

I usually play Minecraft with 'naturalregeneration' disabled; to test the snapshot, I've started new games and made sure I turned that off at the start - also known as "UHC mode"; I've then played the game, and after taking damage, my hearts reappeared.

I therefore tested things, by setting the rule and then deliberately taking damage; sometimes the hearts were regenerated. It may have been after eating.

In the screenshot I made, you can see that the hearts are flashing - which I assure you is due to gaining health rather than taking damage; and you can also see my command showing that the gamerule is currently set to 'false', so that regen should not have occurred.

Environment is for PC details. Use Description for more information about your bug.

That being said, this is a duplicate of MC-121783.