Stone pickaxe does not take durability when mining

I have been playing on a survival world for a bit now in 21w14a, and overtime I have noticed while mining that my stone pickaxe does not take durability. My stone axe and wooden axe both take durability, but oddly, my stone pickaxe always is at 100% durability. I have at least mined more than 50 blocks by now. The pickaxe does not have Mending or Unbreaking. 

An edit: I have made an iron pickaxe, and oddly enough, that doesn't take durability either.