The shaved area is cleaned with antiseptic after the hair is removed
Yep, can't sanitize the area when it is full of fur. As for the boy vacuuming the cat and his age, I am sure he was well supervised and who knows, he could be in the next generation of vets.

As inexperienced as I am at stuff like that, shaving, cleaning and sanitizing to prep for surgery was MY job when I helped SBR on spay day. He taught us all how to wrap and sanitize the tools and how to give shots and prep. I never did the shots but I did the rest including assisting him in surgery. While we were pressed for space, we did prep in a different area while he was sewing up the one he was finishing up.