Yea, /etc/filesystems is documented as only being consulted for -t auto or leaving the switch off entirely. If you explicitly specify a filesystem you expect the system to do what you told it.
But the key point remains, after several replies nobody can point to a way to actually solve a problem that exists on all graphical desktops.
udev is clearly not intended to be modified by the end user. It isn't documented, the files controlling it are written in a way to be hostile to manual editing and the entire subsystem has been churning for years.
Simply stopping the modules from loading isn't a good solution either.
You can't even reliably suppress the icons from appearing on a desktop. I once found a way to do it, it worked until the next Fedora.