I think I finally figured out what was an error on my part to do with shell escapes under Linux wrt using exclude on a sync. And, silly me, I should have know this.
I would suggest the docs be made a little more explicit. For example in the docs https://rclone.org/filtering/
Quoting shell metacharacters
The examples above may not work verbatim in your shell as they have shell metacharacters in them (eg `*` ), and may require quoting. Eg linux, OSX * `--include \*.jpg` * `--include '*.jpg'` * `--include='*.jpg'`
I use bash and used double quotes around my exclusion filter (which included a **) which wreaked haovc for a while.
So, the docs above are correct, but I would suggest a sentence be explicitly added that for bash (and probably other/all Linux shells) using single-quotes is a must as double quotes will expand. Maybe in bold too so people like me will read it
As always, thank you for so much work on rclone, it is an amazing piece of software.