I sort of halfway agree with that.
I don't agree there is any over the top in a (decent) baseball swing but there also isn't much of a "drop into the slot" either. There is simply no time for either in baseball.
To have any chance of hitting a fastball the first move of the bat is for the butt end of the bat to drive straight at the projected point of the ball. The bat, just prior to the butt end driving toward the strike zone, is dissecting the batter's head from the pitcher's view.
In golf that same formula creates a shaft plane halfway down that is pointed inside the golf ball (or steep) where a golfer would have laid off the shaft in line with the back forearm and have a shaft plane at or above the ball.
Then there's the off topic (for this thread) problem that impact happens in baseball with palm up/ palm down where the only way to make that work in golf is to have a super strong grip with both hands.
P.S. I have seen plenty of slow pitch softball players that "drop into the slot" quite nicely. Probably were all good golfers.
While I don't necessarily disagree with this assessment, I want you to look at a picture at impact of both a golfer and a (good) baseball hitter. The weight shift for driving either a golf ball or a baseball require the stiff front leg with the back foot coming up to the toe. Baseball players take an inside out approach to hitting (for the most part), which applies to golf as well.