If health boost is given during when a player already has health boost, the players extra full hearts will reset to empty.

If absorption is given during the time of the hearts reappearing, the time for the hearts to reappear is not used, but rather the golden hearts are given instantly.

Ex of why this is a bug: A redstone loop with the command "/effect @a 21 1" in a command block should give the potion effect of health boost every second. Which it does, but it resets the extra hearts to empty even after being full at a point.