Hunger Effect is gained by eating Rotten Flesh but does not drain hunger bar

Hunger Effect is gained by eating Rotten Flesh but does not drain hunger bar.

In my Java Survival world, whenever I eat Rotting Flesh, I get the Hunger Effect, but even if I move while I have the Effect, my hunger bar is not drained by the Effect.

I go out at night/in a cave/dark area and kill a zombie. I collect the Rotten Flesh and eat it (when my hunger bar is not full) and although I get the Hunger Effect, it doesn't drain hunger even if I move (I know that u need to move/jump for the Effect to drain hunger).