Sometimes there isn’t time to prep before starting, or room to do all the prep, or a ton of other reasons for not doing all the prep ahead of time. Sometimes prepping the other thing you are making while the first thing is cooking is the better use of time. Cleaning isn’t always the best use of time.
Within the context of the original post: if what you’re cooking leaves a huge mess and this is a significant enough problem to complain on the internet about it there was a failure of preparation at several points.
Do all your prep first.
Sometimes there isn’t time to prep before starting, or room to do all the prep, or a ton of other reasons for not doing all the prep ahead of time. Sometimes prepping the other thing you are making while the first thing is cooking is the better use of time. Cleaning isn’t always the best use of time.
That’s why I said depends.
Within the context of the original post: if what you’re cooking leaves a huge mess and this is a significant enough problem to complain on the internet about it there was a failure of preparation at several points.