Different topic: over on the Cessna Pilots Association, there was some discussion about how trim plays into all this. As in, you're 15-20 degrees nose up at Vy, and the engine stops. Suppose you just let go of all the controls. What happens? Some time soon, the plane will be flying at Vy (assuming you were trimmed in the first place). It may have lost a bit of altitude getting there, but it won't be stalled. I'll give this a try next time I get a chance.
Be sure to let us know the results.
I see two issues here though.
First is that people are taught to fly by attitude, and by looking out the window, not by chasing the needles. Especially early in their career, VFR. So they will not let go of the controls but intuitively try to keep the nose up, until they realize what happens. But by then it may be too late.
Second is that even if you let go of the controls, there will be a lot of inertia in the aircraft, and it will take a while to settle in a stable glide (again at Vy, assuming it was trimmed for Vy in the first place). During that period there may well be speed excursions below Vy, and even below Vs, but these, I would imagine, will be at a load factor lower than 1G. I would be very, very surprised if the aircraft were actually to stall in this scenario.
Anyway, the point being that the oscillations before reaching a stable Vy descent may take too long. If you fly the maneuver instead of letting go of the controls you reach that stable state much earlier, and have much more opportunity (read height) to figure out what to do next (whatever that may be).