Currently the app id hash is generated from workdir path only when it's set explicitly and that's for a good reason: the default workdir could be changed (e.g. by creating a TelegramForcePortable) and app id would change what would result in a duplicate .desktop created.
The current code has the possibility of having duplicate .desktop files, too, as it happened, but by specifying -workdir to the same directory as the default one.
There's now a check that ensures the specified workdir is really custom so those duplicate launchers could be removed what should really stabilize the hash.