So that little company is apparently able to do what Apple did not: have it use one method for non-QuickSync machines, and QuickSync if it is available.
You are assuming that is what Apple wanted to do. Apple implementation is very specific and uses hardware for a specific solution. They felt it was much better. Forget that AirParrot is going to support QuickSync - the macs that we are talking about here would never use it anyhow. Apple's goal with AirPlay was to provide the most optimal solution. They wanted a solution that did not involve software and would be so dependent on so many variables - As makes that point by saying that it requires tweaking (without Quicksync). Apple didn't want to mess with all that.
You cannot assume that Apple was going for broad compatibility by any means. That is not what they do.