Why the investigation took as long as it did you would have to ask the PL. The charge against the club is that for 10 years our accounts have been dodgy. That leaves us trying to prove a negative, namely that the accounts are legit. Which involves wading through the source material - the contracts, the invoices, the email trail.
Given the material that the club is compelled to provide I’m not surprised they wanted it heard in private. (A) all such proceedings are conducted in private, and (B) the nature of the material we will be relying on is completely confidential.
Having done nothing wrong and still wanting private information to stay private are completely consistent with each other. I’m sure you’ve done nothing wrong but if someone asked you how much tax you paid last year you’d tell them to mind their own business.