I will try to address the OP's question about waivers. It has been some time since I served, but this is what I am sure still exists in the way of testing policy because the reasoning doesn't change...just the test as it is modified or entirely re-designed:
The CFAT measures one's aptitude as well as general "book" learning". Each occupation has a minimum requirement (cut-off score) that is a "best predictor" of success. We don't/can't predict success for reaching the rank of WO, or of LCol...we can only use the test to predict who will have a sufficient amount of diffiulty in training that they constitute an unreasonable risk of wasting time, confidence, and a lot of money and other resources. We want the surest bets we can get.
Sometimes, however, a person just doesn't do well on the test, or on written tests in general. At the same time, all sorts of evidence suggests that the test is going to be moot because the person has been doing the work all along, and doing it well. If you were interested in hiring someone, would you have your nose firmly pointed at the test results, or would you be inclined to give serious credence to concrete evidence of efficacy in the work needing workers? The reasoning, in that sense, is pretty straightforward...yes?
Test waivers are granted when an officer applicant fails the officer cut-off, but is granted access to training because of other compensating factors. Apart from a hard and specific degree requirement in some Offr MOCs, others have none. All we really want is some proof, just as with the NCMs, that the candidate has a modicum of "learning ability". Anyone who has a degree, for example, has demonstrated to several successive competent raters at one or more universities that he/she has the ability to learn. What we do in our recruiting screening is to select, from any one cohort of candidates, the best of the lot. We want to hedge our bets that the people who ultimately warm the seats in the classrooms are going to be able to process and integrate the learning, not in a four year programme, but in the three and six month timespans over which the typical military occupation training takes place.
Does that make sense?
We may find, in some odd cases, that someone applying for Inf 31 can't seem to pass the CFAT. Now what? Well, wait a minute, the person has a BSc in Cartography. Not half shabby. A degree is a degree, and how imporant is a degree in Cargoraphic Science to an Infantry Officer? Well, sort of, but not really...if you follow. Then why impose on ourselves the impediment of declining this potential INF 31 candidate solely on the basis of an odd test result? The lady/guy can learn, so let's assume that the test result is spurious, or not a valid predictor of success...in this case.
Without going long, that, in a nutshell, is some of the reasoning for granting waivers.