I can't answer for the FAA. As a procedure designer, however, I wouldn't identify a navaid on the chart because the GPS approach is designed and intended as a stand-alone procedure. The only time the navaid needs to be identified is when part of the procedure requires its' use as part of the approach - or, more especially, the missed approach.
Of course, in either of those circumstances, it should be identified with the usual frequency information. About the only other reason I can think that it would be shown without the frequency info is if it's a controlling obstacle in a particular segment of the approach. That's a bit unlikely, especially for a VOR but, if that was the case, I'd expect to see an elevation figure beside the navaid symbol.
Perhaps the reason the navaid actually appears on the chart you refer to is because the symbol was already incorporated on the base topo for the chart. In that event, maybe they simply forgot to remove the navaid symbol.
Why don't you ask them directly?