In contrast to devmode/strict confinment snaps, the shipped command wrapper/adapter of a classic confined snap doesn’t set in-snap command search PATHs
For classic confined snaps’ apps._app_name_.command key the relative path of the executable from $SNAP has to be used, so use bin/desktop-launch $SNAP/path/to/another/executable instead of desktop-launch executable, refer Subtle differences between devmode and classic confinement snaps and the apps.app_name.command key in the Snapcraft.yaml reference