If IR was natural rec leagues would be full of IR pitchers and they're not, they're full of bowlers. And if IR was natural all the rec league Dads would be pitching BP using IR and they don't, they bowl.
For me, working with a young pitcher on their finish is often necessary. I have had pitchers who lead the downswing with a bent/flexed elbow then get their hand behind the ball too early and push into release with a palm up finish. I think it's possible that the palm up finish causes them to work backwards affecting their release. These pitchers often look good to the eye in terms of IR but have no velocity. When I take video of their motion and exam it closely I see that for about a foot after release the palm is going forward/up and not rolling over, this tells me that they are not fully utilizing. This issue can be very persistent and difficult to fix.
For me, working with a young pitcher on their finish is often necessary. I have had pitchers who lead the downswing with a bent/flexed elbow then get their hand behind the ball too early and push into release with a palm up finish. I think it's possible that the palm up finish causes them to work backwards affecting their release. These pitchers often look good to the eye in terms of IR but have no velocity. When I take video of their motion and exam it closely I see that for about a foot after release the palm is going forward/up and not rolling over, this tells me that they are not fully utilizing. This issue can be very persistent and difficult to fix.