If that's true, then the playtest is nothing more than an insult.
WotC: "Let's give them a playtest and let them feel like what they want matters, but we don't actually need a playtest since we know what we want to do anyway."
Some time later...
WotC: "Crap! We've missed two packet releases and are behind "schedule." We'll have to cut their playtest time and now they'll figure out that what they say or do doesn't really matter since everything is still going to be proceeding forward normally. Oh, well."
I mean, what we say or do either matters or it doesn't. If it matters then this shortening is going to hurt that. If it doesn't then we shouldn't be playtesting in the first place.