The issue cropped up again today when I started my PC, a little over a month since my initial post. I do have a pending update for 2024-04 Cumulative Update for Windows 10 Version 22H2 for x64-based Systems (KB5036892) which I opted not to install last night (the last time I saw the recent documents appearing in the Start menu).
When I install the update and reboot I'll report back with whether or not the recent documents populate.
Edit: The recent document section remained empty after updating Windows. Maybe there is some conflict between how that list is populated in Start11 and the presence of a Windows update. I don't know, just brainstorming here.