Good post Pat 42. You sound like one of those fluffy 'modern science' grads with a sociology or psychology degree or suchlike!
I'd have to say it's all semantics. Whether you describe it as unsuitability or as failing doesn't really matter. You wont get into NATS either way so on that basis i'm sticking with it being a test. In the same way that your aptitude might be 'unsuitable' if you don't get through thoses 'tests'!
I refer you back to the dictionary definition of a test ''Any standardized procedure for measuring sensitivity or memory or intelligence or aptitude or personality.''
Ask someone who didn't get in because of it and see if they thought it was a test or not!