In chin-ups, the bar naturally floating towards the fingertips can reduce forearm engagement but strain other muscles.

“But then when you start to apply it to something like your body weight with a chin up, right? 'Cause that's natural for the bar to somewhat kind of float down towards your fingertips. And it actually is a little bit easier to perform the exercise with that sort of like false script little hook grip at the end because you're not going to engage the forearms into the exercise, you're not going to start pulling down. But at the same time while it could help you to perform them better by getting the back more activated, if you have weakness in these muscles.”