It's a funny old world. NCA, or airman aircrew in old money, used to be viewed as a heirarchy. Different course, different entry criteria, and different pay.
No-one would be an ALM if they could be an eng, and all the siggies were volunteers for the role- no question. (This might be where the old loadies with a-levels do the "I only ever wanted to be a loadie" line.)
Now everyone seems to want to be a crewman.
Go figure.
The way you're all treated these days, I'd be ok with a stude who withdrew at the end of the generic course, if the destination didn't suit. Training cost would be peanuts in the great scheme.
CG