Full hunger, no damage taken but I have 9 and a half hearts

I'm recently playing in a solo survival world and noticed that my health is not full though I'm not hungry and not taking damage from anything. I was wearing a diamond armor with enchantments and a gold helmet with enchantment as well because I recently visit the nether to get some blaze rods. I've been noticing it since yesterday and I tried to go to reddit and see if I am the only one who's having the problem and found out that I am not the only person who's having this issue. Even when my hunger goes down and try to eat, It won't replenish that half heart.