[jofer]

The issue is that it's easy to let the oil get to hot while you're chopping an onion. I also do the "prep while cooking" approach if I'm really pressed for time or it's really simple, but it always turns out far worse.

Some prep bowls and a bit of time to find things and chop before turning on the heat may make for more dishes to wash and take longer, but it certainly makes the food a lot more consistent and makes cooking less stressful. No more panicking that you've burned something while chopping up a garnish or letting a pot boil over because your back was turned getting something out of the pantry.