Poose, I agree with the thrust of your point - you will always have square pegs that do not fit round holes. I was awful for the first 6 months at IOT...but two particular members of staff there believed in me. Euan Duncan (RIP) was one who fought my corner at chop time, twice. He made the right choice to back me, of course...
This is why I think it is important to always maintain flexibilty in any recruitment system. We all have strenghts and weaknesses - a strong academic record does not always translate into success; and yet it's no good being a great handling pilot if you lack the mental capacity to see your mission through.
There has to be some form of initial screening and it seems aptitude tests are the best way for volume processing candidates. Should you fail this then you can still have a crack at a flying career but, it then being self funded, this is often too much an ask for many.