I still don't think I understand why one can't just fake folding work and submit it? Will peers be performing duplicate work to confirm?
Yup, there is some work duplication to be submitted, over the years Stanford has developed quite a good system for work validation.

Agreed. People think they can pass one over on their work validation system in F@H? That's been tried for other rewards. In fact, your work is checked through for errors... and rejected if not complete and accurate.