It's text book as far as I'm concerned and the way I was taught to bat, perhaps you were taught differently?

Left knee bent too far forward and stride too short?

I think you're nit picking to be honest. He gets his foot to the pitch of the ball and that enables him to get his body into the correct position to play the stroke - with his body weight going into the shot. The extent of the knee bend and foot position is totally dependant on the length of the ball, if it's back of a length then the foot will be further forward and knee more bent, if if's a fuller length then the foot will be further back and the knee less bent.

Sadly, bowlers don't bowl balls in the ideal position for batsman to play the perfect cover drive!

We can go on about this till the cows come home and still get nowhere and so I'll just say this and discuss it no further. From what I have seen of Vaughan's cover drive - excellent though it is - there are a couple of things that make it short of perfect. YES, the left forward stride is a bit short so that the foot does not go far enough. That means that he has to bend the left knee more and lean further forward at the waist than "traditional" to get to the pitch of the ball, but it probably works for Vaughan because he is a tall man. But the thing I like least of all is the bat and body "arrest" immediatly after the impact of bat on ball with very little and rather late follow-through. In the classical cover drive, the bat would continue in the follow-though arc while the batsman slightly straightens his back along with the upcoming bat.

If you can get hold of any old (and grainy!) footage of Hammond playing the cover drive, you'll know what I mean.