Anonym3572 [deleted] GrapheneOS avoids making changes to that which has a low priority or will be a burden to maintain. UI changes are an example as they would differ from AOSP at every release and would require manually merging the changes and dealing with any conflicts. The project's goals don't align with working on such modifications as GrapheneOS prioritizes security and privacy.
The developers spend significant time and effort on compatibility and usability, as we saw with how quickly they made releases and fixes including a bug they reported upstream, for Pixel 9, Pixel 9 Pro and Pixel 9 Pro XL when these devices rolled out.