Indesign: Author name shown at the printer screen instead of the name of the person that prints.

First, I'd try the inverse of your second test — e.g. bring employee Y into X's workspace, have them sign in as Y and print a job from X, and one of Y's own and see if you get the inverse from X's workspace.

Since we're talking about account codes to the printer, which I doubt InDesign has any access to, I suspect that the printer management software is at the root of this little evil. Based on your testing, I sincerely doubt that InDesign is the culprit here. But anything is possible, I guess, so I'd suggest trying these steps to clear your InDesign installation from X's workspace:

• First try clearing caches and preferences. You can read more about this through this link. The relevant information is roughly halfway down the help page. While this will throw away any custom preferences at X's workspace, it will bring you back to InDesign's baseline to test with the default install for the program.
• The next step would be to completely erase the current installation of Adobe apps at X's workspace, and reinstall from scratch. You need to completely uninstall the program(s) using the Adobe Creative Cloud Cleaner tool, then reinstall the program(s). That's pretty invasive. But if you want to rule out a corrupted install, you could do it.

I understand your desire to sleuth this because it likely involves department billing and the intramural complications that results could spread like wildfire. But I'd look at my printer management software, and maybe consider a reset/reinstall there before I went to the steps above for resetting/reinstalling InDesign. Maybe your Canon vendor/rep can offer some insight.

Hope this helps, and good luck.

Randy

This would be entirely in the lap of the network print manager. I'd suggest some recent update or configuration change has it picking the wrong field from the job header.