I agree with your point about reacting to proper swing mechanics, but I also see value in lazy and sloppy grounders since many in-game hits are not cookie-cutter fly balls or sharp single-hop grounders right to the player. But I suppose mishits are more for practice to stretch a fielder's skills rather than pre-game warm-up routine.Whether it's one-handed or two-handed Watching a coach be lazy and hit sloppy grounders or fly balls sets a bad standard on the field.
To promote better softball,
think it's best for the defense to see two-handed swings because that is the majority of game like visual representation of the ball coming off the bat.
Seeing body mechanics going into the swing is part of reacting to ball off the bat.