Re-hashing this old thread.
gsap in fact does not appear to correctly animate clip-path on ios
You can see this, for comparison, from the following codepen examples:
This version is done using CSS and the -webkit prefixes. I works correctly on iOS
https://codepen.io/adamcoulombe/pen/oNgrMMW
This version is done using CSS, without -webkit prefixes. It does not work correctly on iOS
https://codepen.io/adamcoulombe/pen/BaygPev
This version uses GSAP 3 to animate the clipPath. It does not work correctly on iOS
https://codepen.io/adamcoulombe/pen/oNgrMMW