I'd honestly go ahead and bite the bullet and say these students are lacking in an important intellectual capacity if they can't handle that extremely modest amount of abstraction. If they are successful it is probably due to a solid work ethic.
As somebody who's been programming for most of my life, it was really hard for me to learn to think about this stuff from the perspective of somebody who'd never seen it before. Many thought patterns and cognitive skills that are second nature to us programmers are, for a lot of people, very difficult to learn.