I've worked in a CPA firm before doing both Tax and Audit, and I would say only the most rudimentary details applied. I would say the college degree in accounting applies maybe 5%. The CPA exam isn't much more, if at all.
So what is the CPA exam? I'll tell you. Imagine there's a giant pile of money over there. Naturally, everyone sees it and wants to take as much of that money as possible and run away with what they grabbed, as quickly as possible. The CPA exam is a means of batting off peoples' hands away from the money, of shooing them off, nothing more or less. In terms of “substantial knowledge,” the exam is 100% meaningless. Think about it, there's people who are technically “CPAs” working out there right now who received their license before there was even a Codification.
If we forced “CPAs” to constantly retake the exam to remain “legitimate” every, idk, 5 or 10 years, or sooner there would be no one left in the industry because we would rightfully flee the entire industry. The CPA license is a loophole, and besides that another money-making-racket. That's all it is. Every CPA i talked to knows for a certainty that they would fail the exam(s) if they had to retake them without doing the study nightmare all over again. Yet they're “CPAs.”