The entries were previously accurate, they were loans. "Payday Loan" is perhaps more specific, but it is still a loan, there was no inaccuracy in the previous logging.
They do have an impact on my credit file, as other lenders see payday loans as a sign of financial instability (which I don't really agree with, not paying them on time should be a sign of financial instability, but lenders are obviously free to make their own decisions). I was told directly by Halifax that these entries were why they declined my mortgage application. Had they been listed as "Loan", as they were previously, this would not have been the case.
A couple of years ago, Wonga did not report satisfied loans to CRAs, then changed their policy selling it as helping you to show positive credit usage for all agreements going forward. The part I have issue with is that this new change is retrospective, and seems to be barely any better than had I defaulted on a mobile phone contract or similar, when I have done nothing wrong. One could almost wonder if Wonga were incentivised to keep you from mainstream credit so that they retain you as a customer.
To me this is a breach of the FSA principle of treating customers fairly, as the change is retrospective.