And you are wrong about golfers not using the static position holds to help develop a feel for the swing. There are certain key swing points/positions that enable a great golf swing, and a good instructor will have you hold these positions to help develop a feel for each. He will even phsically move your arms or legs or shoulders, setting your body in position like you're a mannequin. He ask you to hold that pose and look at your wrists, your arms, the club, the ball, etc....pay attention to how everything feels at this point. He'll have you bring the club back super slowly and he'll stop you again, repeating the holding process, correcting any body alignment issues, asking you to focus on how everything feels. This swing grooving might be all you do for 30min. Then you'll hit some balls, intermittently stopping in your backswing or downswing to focus on how every feels and looks from there, from the top of the swing, from the hinge point, from a foot before ompact, etc....
NOPE! That's not the way it works. The positions are produced not by holding the position and looking at it for minutes at a time and ingraining it, but by the instructor altering the GRIP on the club, the posture of the player, his feet and body alignment, and how far or close he stands from the ball. There's also the height of the player, body type, and how the weight is distributed on his frame. THAT is how positions come to be.
Case in point, Jim Furyk swinging the club vs. Rickie Fowler. https://www.youtube.com/watch?v=AgwVArw9xa8 Fowler: https://www.youtube.com/watch?v=2Q7V9XY7Ipw
Jon Rahm hand and wrist position at address, at the top of the backswing and down into impact. He and Dustin Johnson have the same BOWED wrist position at the top as we're talking about in the pool grip. Other players do NOT.
https://www.golfdigest.com/story/jon-rahms-short-swing-is-long-on-power
It really is a very effective way to produce a great and consistent golf swing. I'm sure baseball players use similar slow motion or holding positions to hone their swings also, but I've never taken professional batting lessons, so I have no experience with that.
Oh sure they do. With a baseball coming at them 85-100 mph from the knees to the chest and everything in between with balls dropping down and curving all over the place. Get real.
It's not about getting into or holding a friggin' position during the swing. It's reactive to just getting the bat on the ball so it doesn't end up being a called strike 3 or getting hit with the ball. It's a wide strike zone and sometimes has to be swung on and hit outside of the strike zone.
It's not a muscle strengthening excercise. It's a method of training the brain to recognize how certain muscles and positions are supposed to feel at keys points in a process. It can be applied to any skill that involves muscle memory and hand coordination, from pool to tennis or golf or baseball, or from violin to guitar or piano or whatever.