No legal expert, but my view is this: the PL has gathered more "evidence" in the form of emails, spreadsheets and the like that have extended the time period of the allegations from the limited UEFA investigation to the full ten years. The PL and the club both know the evidence to prove or disprove the most serious allegations is external. The PL wanted it (and they know it exists because it was provided, for the limited period, at CAS) and the club didn't want to provide it (or will claim they made their best efforts but the externals refused). So the PL could either drop the allegations without seeing the counter-evidence, or just go ahead and refer the allegations knowing that, probably, the club miraculously provides the necessary counter-evidence at the panel. Clearly, dropping everything without being satisfied by counter-evidence would set a terrible precedent. I don't think the PL had a real choice. Explains the non-compliance allegation too, btw.