I’m going to be blunt here.
As Person B, I would inform Person A that he is wasting time making test cases at that point. When you have to build and maintain 620 test cases for a system, you will inevitably spend more time maintaining documentation and blindly executing steps than actually testing.
Rather than focus on the scrutinizing the current behemoth, the team’s energy could be better spent in making the process more interesting, less lengthy, have less maintenance, more efficient, able to find more issues, have more testing, and just be better.
Rather than test cases, you could use more session based testing, automation, checklists, and so on.
Out of curiosity, has anyone’s client (or auditor for that matter) EVER asked for test cases? In my experience, the customers, clients and (good)auditors only want to know how something was tested rather than if the test documentation matches some random standard.
Thus the test documentation is something I can look back on and give the answer to “Was this tested?” by “Yes, in several ways.” or more frequently, “Yes, but we seem to have missed this one specific configuration.”