This is not about GA vs Cadet. It is about hiring a fresh CPL over someone with years and thousands of hours experience. Jetstar recruits don't just come from GA. Many (most?) come from airlines with significant jet and/or turbine time. I could understand a scheme to supplement direct entry during times of high demand, but to hire a cadet before interviewing an experienced applicant wouldn't make any sense other than financial (and maybe they won't).
Those who don't fly the line just don't realise the value of a good experienced First Officer. They're excellent value when they prevent an incident or accident - which does happen. Did they ask the line pilots thoughts?
A cadetship is an accelerated process into a job that most others would spend years working towards. In other words, and with all due respect to GA drivers, cadetships will only take the brightest people who have the aptitude to learn quickly.
Umm, I think you just skip the experience bit, which naturally accelerates the process a little.