I'm not answering the question with this post but you can't think of any downsides? Surely if singles were the same as a set you would see singles in the main programme?
Think of it in extreme terms: if you did 1 squat today, 1 tomorrow, 1 the next day, etc. and it took you 5 days to get your 'set' would it be the same as 1x5? I'm guessing the potential problem would be not causing enough stress with singles. But i've not tried them so take it for what it's worth