There is no reference saying you cannot do it.
Personally I do it like that every time I start the APU and want the bleed, like shoot and forget, so I can continue with the preparation. Except if I suspect that the guy in the left seat could dissaprove it. Then I Prefer not to start another stupid argument where there are two options: I am wrong or I am not wrong but anyhow I have to act as if I were or else destroy the good atmosphere. ( if you flew in my airline you would understand what I mean)...