I think a surgery prelim is a great way to limit options. In the next match, if this guy gets interviews, will the prelim allow him to go to all of them? All over the country? Hard to know, hard to plan for. Several friends of mine had to refuse interviews in remote locations, and ended up not matching. They are bitter about that. Similarly, signing that contract means you can't get out of it, a lot of the time. My perspective is that if you don't match once, do a research year (and do it hard), or extend graduation (and still do a bunch of research). The nice part about that is that you'll be able to go on all your interviews, you will buff your CV for your future, and you'll hopefully make connections in the field you want to go into.
Doing a prelim surgical year for somebody not interested in an advanced position in surgery, or even in programs that are advanced and require a separate internship, is a waste of time and an incredible waste of effort, misdirected into a grueling year rather than their actual goal; securing a residency. If all else fails, it's very likely this guy can get a prelim surgical year in NEXT years match, so he can still practice medicine in some capacity in his future.