Can't speak for the 737 but the A320 SOP's infers that we do not disconnect the ramp engineer following our start up until the PM has completed their duties, right down to confirming the doors are armed. A number of the items in the after start scan could get you grounded, so even if it were not a requirement, seems sensible to me, especially when you consider that it only takes about 8 seconds to watch the PM complete their duties including set the flaps correctly. Of course it is in the checklist but that should be a last line of defence not the primary means. I beleive the 330 may not give you 'no blue' for takeoff if they're in the wrong position but I could be wrong.
I hate to say it but these guys are not the first to commence a takeoff with the wrong/no flaps set, nor will likely not be the last.