When you shear a Sheep it grows wool like 1-3 seconds after eating from a grass block.

I noticed this on a World when I put sheep in a mob spawner and then sheared the sheeps that came out of the mob spawner, I shear the sheep, then it eats grass and it instantly has Wool again.

This seems to affects all sheep . Maybe a problem with updating the 1.17 World to 1.18.2? I don't know. By the way Tick speed is default (1).