They should, and do, look at head to head matchups. They also look at overall schedule. Wake has nonconference wins over Gonzaga, Richmond, and Xavier, all of whom made the field, and a victory against Maryland. Clemson is 30ish in the RPI.
For the record I do think VT should have been included this year. But the committee also has sent a clear signal that strength of schedule, particularly who you play out of conference, matters. Seth Greenberg continues to schedule awful teams out of conference and year after year is on the "snub" list. Einstein's definition of insanity is continuing to do the same thing and expecting different results.