My take is the exact opposite. I think it was absolutely pre-determined that Lampard and Harrison would make their season debuts. You could see it coming from a mile away, and it was totally expected. Biggest game of the year, biggest crowd of the year, Harrison's mum was even in town, and they thought Lamps would get a hero's welcome.
The front office had this entire thing planned out from a marketing perspective, and I think those 2 subs were going to happen no matter what (which really leaves PV with only one sub to use at his discretion). They were totally tone-deaf about the actual play on the field (and the need to sub much sooner). Advertise the hell out of the game, boost ticket sales, get the big names in the game, have the stupid halftime "show", give away freebie balls at the end, etc. All of it was gonna happen like that regardless of the actual game. I'm sure they weren't expecting an historic loss to kill their vision of a great day at Yankee Stadium though....