Consistent Icons for Zoom in Gnome Wayland on NixOS

I use zoom on Gnome Wayland in [NixOS](https://nixos.org) ([dotfiles](https://github.com/joshrule/config)) . The problem I’m trying to solve is that while I can see the zoom icon in the launcher/overview: I get the default application icon everywhere else: I had a similar problem with [foot](https://codeberg.org/dnkl/foot) , because the desktop entry was missing the line StartupWMClass = foot. I wrote a [custom desktop entry](https://github.com/joshrule/config/blob/ba01eb5dff7f9274ceffae2638efea4ed7577723/users/rule/home.nix#L150-L166) , and that resolved the problem. Now, the default Zoom.desktop file already contains StartupWMClass = zoom:

ini
[Desktop Entry]
Name=Zoom
Comment=Zoom Video Conference
Exec=/nix/store/v651rqca7bjrbvgc1760qcskj7lcgapn-zoom-5.15.2.4260/bin/zoom %U
Icon=Zoom
Terminal=false
Type=Application
Encoding=UTF-8
Categories=Network;Application;
StartupWMClass=zoom
MimeType=x-scheme-handler/zoommtg;x-scheme-handler/zoomus;x-scheme-handler/tel;x-scheme-handler/callto;x-scheme-handler/zoomphonecall;application/x-zoom
X-KDE-Protocols=zoommtg;zoomus;tel;callto;zoomphonecall;
Name[en_US]=Zoom

I've tried changing the capitalization (i.e. StartupWMClass=Zoom), but that doesn't solve the problem. Also, running desktop-file-validate on Zoom.desktop (see [this question](https://unix.stackexchange.com/questions/41135/png-image-not-displaying-for-desktop-icon-on-fedora-16-17-with-gnome)) warns of a couple deprecations, but gives no errors. Similarly, I see no errors in ~/.xsession-errors. In addition, looking glass (i.e. Alt + F2 “lg”) doesn’t report a known wmclass nor that Gnome used Zoom.desktop to launch zoom. What is going on here, and how can I consistently use the zoom icon throughout Gnome?