Consistent Icons for Zoom in Gnome Wayland on NixOS

Question

I use zoom on Gnome Wayland in NixOS (dotfiles). 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, because the desktop entry was missing the line StartupWMClass = foot. I wrote a custom desktop entry, and that resolved the problem.

Now, the default Zoom.desktop file already contains StartupWMClass = zoom:

[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) 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?