I’ll admit, I don’t have perfect pitch. I do however have 2 friends with perfect pitch and a teacher with it. One of my friends says it is useless (they also play an instrument). The other 2 find that they are the exception to the “useless” rule. The other friend is training to be a composer and the teacher teaches students relative pitch with it. I’m sure if you used it properly it would indeed help with improv and learning. However, I don’t understand how it would help you play in tune. I feel like that’s more of relative pitch (which is what most professional musicians use). I also play a fretless instrument and I feel like playing in tune is more of muscle memory and subtly adjusting your fingers by the millimeter, and less about having perfect pitch. The areas between using perfect and relative pitch blurs a little though (which I think you might be confusing(?)).

For example, you can go like: Wham! “Oh that’s a little too high” and adjust (relative pitch)

Rather then: Wham! “Hmmmmmmm, that’s an an E not an F” (perfect pitch)

Fun fact: Itzhak Perlman promotes relative pitch and knowing the distance between notes rather than perfect pitch.