Theres lots that dont have the button one of the ones i was looking at was the msi b450m vdh or the m.2. I think itd be any other board thats not on the list above.
I was talking specifically about the Mortar but it would probably also apply to THOSE THAT HAVE THE FEATURE. I'd agree that a board without a button probably doesn't have the feature... and vice versa.
The list TJ linked should make clear which have it.