USG FLEX 200 - Blocked URL Keywords to block download of certain files

I thought I could use Blocked URL Keywords to prevent downloading of specific file types (e.g. .exe, .scr, .bat files).

I have a working active Profile for Content Filtering and the Forbidden Web Sites is working for domain names.

However, Blocked URL Keywords doesn't seem to do anything.

For example, to block .scr files, I've tried:

*.scr*
*.scr
/*.scr
*/*.scr
*/*.scr*

The idea is to block access to e.g. www.anydomain.com/path/to/someFile.scr

And I do have "Enable HTTPS Domain Filter for HTTPS traffic" checked.

But nothing's being blocked. Am I doing something wrong?