The App Grid is Gnome default. So, this is on every System with Gnome. Sounds all a bit mysterious.
It does, doesn't it? I wanted to compare some things in Zorin to how they've been behaving in Nobara, so I'm back again for the moment and can answer the questions you posed before.
As mentioned, I use the application grid, and it's intact.
$ gnome-shell --version
GNOME Shell 43.9
Zorin Desktop and Zorin Desktop on Wayland.
When I restored my backup from having hopped to Nobara, a bunch of system updates were waiting for me. When I installed these, Zorin reinstalled zorin-os-desktop, which doesn't bother me, but also put back Pulseaudio. I went through the same steps as before to remove PulseAudio and switch to Pipewire, and once again zorin-os-desktop is gone and yet I still have everything functional, so whatever is happening reproduces. If anyone is feeling curious enough to try this in a VM, the steps I followed were provided by this article:
The article has the user choose between wireplumber or pipewire-media-session. I chose wireplumber.
Well, I found a difference! Would've been easy to spot if I'd done this on a new installation I hadn't finished adjusting: The settings menus are broken without zorin-os-desktop. I still haven't found anything else, but there's no settings shortcut in my application grid and right clicking on the desktop and choosing settings or Display Settings does nothing at all. So, mystery solved, and it looks like I can't keep Pipewire on Zorin, at least not using those steps. The settings menus are kind of useful, after all.
Of course, now thanks to a ton of rather questionable dependencies, I get to go back and re-remove stuff like Cheese and Brasero. Weird that zorin-os-desktop doesn't care about removing those, but insists on putting them back if I'm to reinstall it.