I'm not saying anything about the size of the short position here (naked or otherwise).
However, also consider that fails to deliver are only reported when cleared through the DTCC. When the MM's ex-clear no FTD's are reported, or more precisely, they do not have to be reported.
The SEC actually supports the MM's ex-clearing away from the DTCC. The SEC goes as far as to state that ex-clearing between MM's is considered proprietary therefore they do not have to disclose it, as disclosing it would reveal proprietary trading strategies.
Not reported to the SEC = not on the SHO list.