We haven't yet seen what Wally's excuse will be tomorrow. He could say
'I was waiting till you asked for those unnecessary changes you didn't say you didn't want.' or maybe
'I was still doing the unnecessary changes you asked for with last weeks analysis,' or maybe
'I was waiting for you you ask for some necessary changes.'
One-up for the PHB! Wally, though, is the winner among the losers: he has the most fun with all the sh!t the PHB, Catbert, etc. put the engineers through. In other words, he makes the best lemonade with the lemons life throws his way.