Taming Whisltes not reliable in decks

This problem it 100% repeatable. Just follow the steps below

I have a fighting deck equipped with a specific pet in it.
I have an alternate deck with taming skills and a blank whistle.
I have blank whistles in my inventory.
Other than the taming whistle, my equipment list is the same for both decks.

I fight using the equipment and the pet from the taming whistle in the fighting deck.
I go out of combat, dismiss my pet, swap decks to my taming deck with the blank whistle, go back into combat and start taming.
If I am successful taming a creature, the whistle in the taming deck changes from a blank to the whistle with the new pet ... and that's not the way I thought this was supposed to work.
It was my understanding that the items in the deck's equipment "inventory" should not change unless I modify the deck and tell it to use current equipment. So as long as I have blank taming whistles in my inventory, I should never see a populated whistle in the equipment list for the taming deck