I see no reason to do that bleed on while APU starts thingy. I know things get hectic at times in a turn, but there's a memo right there on the screen to remind you that you turned on the APU, plus a few coloured switches on the overhead that normally aren't coloured, in case you forgot about it, plus the extra noise. Dunno, maybe that's just me.
While we don't do that, we do turn on the APU and as soon as it indicates it's available we put the bleed on, after the external air caveat has been covered