I agree with you that they should put notes like that in the game. I requested several of them on the PTR.
It it did not slip their mind or go unnoticed. They were asked to put it in the description, and deliberately chose not to.
That makes it not a bug, even if it was a stupid decision on their part. I do not expect them to add it later, because they were already asked to, and they decided not to add it.
So, you have to go read the patch notes if you want to find out these things. This is the model Blizzard prefers, apparently.