Clear Recent Files Not Sticky
Illustrator>Preferences>File Handling & Clipboard>Change Number of Recent Files to Display from 20 to 0
Re-Open Illustrator (Recent Files Gone...What I want)
Illustrator>Preferences>File Handling & Clipboard>Change Number of Recent Files to Display from 0 back to 20.
Re-Open Illustrator (Recent files all return)
Expected Result: When I change back from 0 to 20, I expect all of my recent files to be gone.
Actual Result: Recent Files return when I change the settings back from 0 to 20.
The setting you are referring to only controls visibility – does not clear the list. Sure way of clearing the recent history is to clear Illustrator preferences.
Deborah Dewhirst commented
Why should there be a need to trash all preferences just to clear the recent files list? Can't Adobe just provide a button for this purpose on the Home screen?
Meanwhile I have found a slightly onerous solution that avoids trashing all preferences if anyone is interested. https://community.adobe.com/t5/Illustrator/Clear-Recent-Files-in-Illustrator-Issue/m-p/10708928#M150709