The new rule was after 2012/13 iirc, after Mancini had left, so I don't think the club has a problem with a literal reading of the contract he had with the club.
I think the more serious allegation, although unlikely to succeed imo, is that, because the club apparently made some payments to Mancini for the AJ contract and was apparently involved in negotiating the AJ contract, the club should have included the AJ remuneration in his club contract and, because they didn't, knowingly understated expenses in the accounts (the first tranche of allegations along, probably, with Fordham and Toure).
Does that make sense?