The thing is - the bank referenced in the story has COBOL programmers, but they kept recalling the effective COBOL programmer.
That's the issue with self-training for mission critical systems. Sure, some people can self-train, but a company doesn't want to pay people to learn on the job, while thwey are counting the beans.
The only signal worth paying attention to is industry salary trends, but reporters rarely have the time or incentives to actually do real reporting.