Health does not regenerate fully

Health does not regenerate fully after eating, it only regenerates up to 9.5 hearts

steps to produce:
1. Create a new world (preferably hardcore)
2. play for a while (1 or 2 days in game)
3. lose some hearts
4. Eat to regenerate health

observed results:
health does not regenerate full, it only regenerates up to 9.5 hearts

expected results:
health is completely regenerated by eating food

NOTE:
This bug may be difficult to reproduce, it seems to only happen in hardcore mode but I'm not sure.
It only happens when eating, health is completely regenerated with a regeneration effect or instant health.