The official got it spot on but, if the scores had still been 2-2 with the visitors pushing for a winner, I'm pretty sure that same old line about 'Fergie time' would have been trotted out.
Still, conspiracy theories seem to go with the territory with United. As Wayne Rooney hobbled off, clearly injured, with the scores level, it was hinted on TV that it was a tactical withdrawal to allow him to miss England's friendly in Sweden. Chasing a winner to ensure his side could remain top of the table into the international mini-break, I'm pretty sure Sir Alex's first thought was to lose one of his very best players with the striker's midweek involvement for his country dictating his decision.
When teams time-waste, referees are certainly within their rights to stop the clock. I think there are often not enough minutes added at the end of the first half when an injury or two has occured. It's often only two minutes when this has happened which, considering a minimum of one can be displayed, is clearly insufficient.
As Sir Alex has intimated, it would be beneficial if there could be a discussion about time-keeping without any accusations that it's somehow all a grand ploy to ensure the Reds can score late goals. It is an emotive subject, perhaps because nothing hurts more than conceding to your cost in injury time, but it's one that he feels does warrant attention.