Depends on how many things you are making at the same time and the volume of mess.per item.
Cleaning as you go is the best, but sometimes you can’t stop stirring or chopping or peeling to do it.
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.
That’s why I said depends.
Some things involve multiple utentils and dishes at the end of the process and there is no amount of preparation that avoids needing to clean multiple things at the end. Like making a cake will have the same amount of dishes when you put it in the oven, more if you do additional prep in small bowls ahead of time.
They are really just complaining about the amount of things to clean and the mess that some stuff makes as part of the process.