Remember that all these guys are capable of hitting homeruns, so maybe their focus is staying relaxed which is a good point.
On the other hand, if you want to teach your dd to hit it hard, what good will it do to teach her to take nice easy swings that result in soft line drives to ss? Do you think she'll ever hit one out with that approach? Maybe by accident. Then if she trys to hit it out she'll be in unknown territory. I say, perfect practice makes perfect. If you want to hit homers, practice hitting homers.
So yes, I can say "imagine how good he might have been."
Teaching your DD to hit the ball hard is a good thing, completely agree. And that's the mindset they should have. Having HR on your mind all the time is not good, the intention should be to hit it hard..IMO. Staying relaxed is key for any hitter. Staying inside the ball is also good practice. The pros practice staying inside by going UTM and Oppo.. so that they can hit the ball hard, stay through the ball. Which results in more extra base hits, hard hit balls, HR's. Need to look at the big picture. Hitting Hr's don't happen just because they say "I want to hit HR's".