Either way, it really does not matter. The POPLA decisions not binding on you and has no bearing on anything going forward.
I will place a £100 bet that if you follow the advice, this will pan out as follows...
You ignore all the useless debt recovery letters as the debt collectors are powerless to actually do anything except to try and make the low-hanging fruit on the gullible tree pay up out of ignorance and fear. You can safely ignore all DRA letters and we don't need to know about them.
Eventually, you will receive a Letter of Claim from DCB Legal which you should show us and after that, an N1SDT Claim Form from the CNBC, which must be responded to.
After defending the claim, it will eventually be struck out or discontinued.
You may want to complain to POPLA about the mention of some unrelated name in their appeal rejection. It raises the possibility that the assessor was looking at the wrong appeal when making their assessment.