I just tried setting up the same scenario and it appears you might be right. Wildcards seem to be okay, but macros are not being evaluated. I had a file named 20180608classic.prn. My input file and monitoring are set to 201806&[dd]classic.prn. Never picked up. If I renamed the file itself to 201806&[dd]classic.prn, then monitoring did kick off, but the process would fail because Automator did evaluate the input to be 20180608classic.prn. I will enter a support ticket to see if this is a bug or by design.
As a workaround, I was able to use wildcards in the monitored file specification, so I could enter *classic*.prn which allowed Automator to kick off the process, and when the process runs, it only picked up the file with the correct date, 20180608classic.prn. Hopefully this work around is suitable for now.
I will update this topic once I head something from support.