breaking coral fans with silk touch pickaxe does not decrease durability on pickaxe

Breaking coral and coral fans with silk touch pickaxe does not decrease durability, which means endless mining of coral and coral fans without breaking the pickaxe.

Recreate:

1. Enchant diomand pickaxe with silk touch
2. find coral reef
3. mine some coral or coral fans
4. durability will be the same as you would not break anything