This doesn't make a lot of sense as an explanation for the policy—if there were more doctors trained that doesn't require that they find jobs, but it does make

This doesn't make a lot of sense as an explanation for the policy—if there were more doctors trained that doesn't require that they find jobs, but it does make it easier for hospitals to replace their doctors if and when they need to, and likely at a lower price. If healthcare costs were the reason I'd expect the government to cap the number of doctors they employ now, not try to guess how many doctors they'll wish they could employ in six years.