I thought you had to press and hold the slate button to get a tone? I suppose you could glue it open.
The settings for AUTO imply that in automatically inserts a slate tone at the beginning (or beginning and end) of each take.
I just tested this and it does seem as if the SLATE button is NOT functioning in AUTO mode.
BUT - there is a small pulse on channel 3 if you do press it...perhaps a bug?
EDIT: Rethinking this a bit - the small pulse I see in the levels is from the sound of me pushing the slate button with internals which I had active and leveled up.
With levels all the way down - you still get the auto slate tone,
but otherwise SLATE has no effect if pressed in AUTO mode.
So - by using the AUTO slate feature - you can disable the button. (at least in theory!)