I don't think you understand what "work restrictions" are.

Work restrictions specify things you should not be doing because they pose a danger to your health. For instance, if you've had a recent back injury, a doctor may give you a work restriction like, "No lifting over 10 lbs." in order to protect you from re-aggravating it. "No work restrictions" in Fetterman's case simply means that performing the job of senator is not likely to pose a danger to his health.