No way that would ever happen. Mass-scale is right. Do you have any idea how much it would cost Apple to test each computer ordered for "at least one day" before delivery? People were already complaining about ordering the ATI and having to wait 3-5 weeks for delivery. How much longer do you think it would have taken to test each one for "at least one day" before shipping?
And I know you'll say, "But I was just talking about testing the replacements for the malfunctioning iMacs." Either way, it's probably cheaper for Apple to replace or repair the iMacs of customers who complain, and, for those iMacs that are replaced, to refurbish and resell them at discounted prices later.
Gotta respect that bottom line.
You know you are probably right, now that I think more about that. They may do that, and wait for people to complain for now, while they work on a firmware fix and issue it out when the fix is done.