A common response to golfers doing speed training (e.g. swinging as fast as possible) is to question the accuracy or strike quality. That misses the point of the exercise .
(a short thread)

Yes, during rounds you are balancing distance and accuracy. Most of your practice time should consider this balance.

But it's hard to speed if you are ALWAYS focused on that balance. To maximize speed, a small % of your swings need to isolate speed at the expense of accuracy.

The goal during speed sessions is to drive top-end speed up, and this requires you to go all-out (which won't happen if you are concerned about accuracy).

By increasing top end speed, cruising swing speed will also increase. i.e. your "80%" swing is faster than before.

So yes, accuracy & strike quality will probably be worse than usual when a golfer is swinging with max intent. But that 1) does not mean they intend to do that on the course and 2) is usually being done strategically to target increased speed with a small % of their total swings.