That qualifier, "for the given compensation", being implicit is what confuses things. It would make sense to say something like, "There is a shortage of skille

That qualifier, "for the given compensation", being implicit is what confuses things. It would make sense to say something like, "There is a shortage of skilled workers willing to work for $1 per hour", and no-one would be likely to argue with that - there certainly is a terrible shortage of such workers! But that makes it clear that the problem is the compensation, not the available workers. If you just say "There is a shortage of skilled workers" without that context, it becomes a incomplete statement from an economics perspective, and the GP is essentially objecting to that and pointing out that once you take the necessary context into account, the problem is not some sort of more general shortage of workers.