All depends on the MOC. Also depends on physical reality. I.e. If a particular representative only had 15 applicants total, they probably COULD interview every one of them. On the other hand, if a representative had 125 applications, they probably couldn't physically interview that many. You have to realize that there are on average, 10,000 applicants to the air force academy. With 453 representatives; assuming they were all equal, that would be a little more than 20 applicants each.
So many of the representatives and even senators will have their staff pre-screen the applications. Some will rank their applicants with a combination of GPA + SAT/ACT + Sports + Leadership. They will then interview the top "X" number of applicants.
This is just an example. The MOC can do whatever s/he wants to do. Interview all; pre-screen; only look at records and no physical interview; etc... It's totally their choice.