Yeah, there were 3 eating mechanics:
1) you run around with open mouth and eat everything, it was too easy
2) you have to wait for animation to eat the shroom to finish to move again, it was too hard as The Old Man keep getting hits upon you
3) the final implementation: you can activate bite at any time and move while animating, but to actually consume mushroom you need to be the right size and stand right in front of it when the pop up shows up, so the gameplay is more dynamic and more skill needed.