I think Perez's "United took hours to reply" thing comes from the idea that the clubs did a deal in the afternoon. However United's statement makes clear that we considered the DdG move dependant on us getting Navas as a replacement.
The contract with Navas was still being changed until after 11pm and one of the Spanish papers in the immediate aftermath described it as, "Navas was 100% happy with the transfer at 11:55." 5 minutes before the deadline.
It sounds like that's when we went ahead with loading the DdG paperwork to FIFA. Our "it was done by 23:58" statement. Did Real Madrid have to wait for us to file to FIFA before they could do their paperwork? Who knows? Who cares? We acted reasonably by making sure we had a replacement.
Incidentally, the Coentrao deal was more or less identical, but in reverse. We filed the papers for his loan deal so late that Madrid couldn't bring in a replacement. I blamed us for that screw up.
There was a deadline, if Madrid had wanted DdG badly enough, they'd have made sure it happened.