When an application got renamed by flatpak-builder without knowing it, it will still send its original value as desktop-entry breaking the mapping. If the PID of the service matches the window owner's PID imho it's fine to assume it's a match.

5.16?

• My spotify snap has media controls in its context menu and tooltip now
• p-b-i (where the host binary doesn't match the browser window) still works for both Chrome and Firefix
• VLC player still works