.sync-exclude.lst apparently does nothing

Nextcloud version: 18.0.6
Operating system and version: Ubuntu 18.04
Apache or nginx version: 2.4.29
PHP version: 7.3.24

The issue you are facing:

I have a folder called gmusicbrowser, and I only want to sync a file called gmbrc. There are folders in this folder, and files called gmbrc.bak and gmbrc.bak.20201224.xz.

I have a .sync-exclude.lst file that looks like this:

icons/*
layouts/*
plugins/*
gmbrc.bak
gmbrc.bak*
gmbrc.bak.$
gmbrc.$.xz

I followed the patterns listed in the documentation, and I tried asterisks. None of this works. If I have a file called gmbrc.bak.lol, or gmbrc.bak.00000.xz, Nextcloud will always sync the file.

Is this the first time you’ve seen this error? Y

Are you referring to a client which does not respect the exlcude file?
My current unterstanding is that the whole .sync-exclude.lst mechanism is only handled by the (desktop) client, but not if you mount the stuff using WebDAV or the file is already present on NextCloud server.