Why do you feel like you would be less clean? Like peas touching carrots on a plate? You have 1 body.
IMO the different sized towels are all towels and are sized for convenience. If you only wash your hands you don’t want to have to use a blanket to dry them. When you wash your body you don’t want to use a box of tissue sized towels to dry off. It isn’t about contaminating part of your body.
Maybe they are out of them because some ghoul took all of them to clean their car? One self entitled customer.