A feeder route is neither fish nor fowl in the wonderful world of the FAA. It is listed on the 8260-3 as a terminal route, but without an IAF. And, it is not an airway. So, is it a non-segment part of the approach? Obviously, it is a part of the approach or it wouldn't have a course, distance and altitude.
Rock science this is not. He should have flown his clearance. Is there anyone here whose CFII told a student to do WETF he wanted to do instead of the clearance he got from ATC? I think not. It's all on him. Read back the clearance, get your release, depart, and contact departure.
Not much of this flying stuff is rocket surgery...but there are people whose certificates say “English Proficient” that clearly they aren’t.
