Is not possible to get a efficiency 5 in diamond tools while enchanting. Netherite and Iron tools works, I suppose wooden tools works because the issue is being creating in some numeric management that Minecraft does when getting the level for tools. I do not think this is the original intention, I rather see mote accurate having netherite tools not being able to enchant with efficiency 5 or either having diamond tools capable to enchant with efficiency 5.

For recreating this issue in vanilla minecraft you can either test for along period until you are in a really small change for been a coincidence or you can make some RNG manipulation and get the same conclusions as I did.