I've successfully updated my '23 SC SEL Premium to this latest update (took ~hour) and I'm disappointed with AA in full-screen.
I found turning off split-screen for Android Auto makes the AA interface buggy when trying to switch between apps, more sluggish and there's a loss of UI features I depend upon when trying to use other apps I run within AA at the same time.
For example, in full-screen AA an app I use every time I drive no longer shows its icon and I have to completely switch out of maps, etc. to load it from the entire list of apps to not only run it, but even just switch to it while it's running which makes AA very cumbersome and distracting while driving. I expected the shortcut icon for the app to appear on the left, but it doesn't. In split-view the icon always shows up at the bottom as long as it’s a recently used app (which it always is). There's also some other UI features missing including being able to play, pause, etc. at the bottom of app windows with a media app I use while using other AA apps.
I ended up having to turn off full-screen AA and very fortunately got those UI features in AA back to the way I want it and apps/UI is less sluggish again. Some apps that worked fast are now a little bit slower I think even with split-screen back but I'm not sure just yet.
Not counting on Google (and/or Hyundai) making AA less buggy for the full-screen problems I'm seeing anytime soon, if ever. I also notice that the location I'm at flickers in AA Maps app now whether I'm in split or full-screen. It didn't do that before the Hyundai update. Oh well, at least now the little Hyundia map thing in split-screen stays in dark mode.
Granted, some of the apps are 3rd-party side-loaded into AA, but they worked much better until I use AA in fullscreen. So, it's probably on Google, not Hyundai, or maybe a combo of bugs from both of them that makes full-screen flakey for my uses. YMMV, of course.