Yes, one of the problems with moving and then standing straight up when you hit is trying to stay balanced through the whole shot without falling over. Thus the body executes compensating adjustments usually in the fine motor area which is very subtle and goes largely undiagnosed into the "why" someone is falling backwards.
Exactly right. Approach shots or short balls are often plagued at the club level with huge swings. It is very deceiving to see the pros hit these hard balls and think that we can just roll out of bed and hit them too. We may get one or two but we also miss a lot more. It is the one and two that we make that have us going to the well one too many times.
As you indicated, the key to power especially on the approach shot or short ball is not force or swinging harder, it is all about timing (including footwork). Making clean contact means you hit the ball right in that sweet spot of the racquet and with good timing/weight transfer the ball zooms by the opponent for a winner.
When hitting an approach shot or a short ball, timing, clean contact and placement are the most important things to practice and memorize.
Yup, on the footwork, you are preaching to the choir.
Good job on the insight