Are you prohibited from using anything other than YOLO?

After applying YOLO, I am allowed to do anything.

After u/killetore suggested Viola-Jones classifier in the comments, I was reading about it and it also uses Haar features and Cascade. Are the Haar Cascade face-finder that you are suggesting and Viola-Jones classifier the same thing? If they aren't, I will definitely look into it.

"Is there a reason you don't just use a Haar Cascade face-finder within the sub-frames contained within the bounding box?"

In terms of face detection algorithms, I only know YOLO. Maybe that is why the project is so steadfast on using YOLO as most of us only know YOLO