Yes, it appears that an update to WinSCP is what caused this change in behaviour.
Yes, un-checking "resolve symbolic links" does appear to make the file filter work as it did before.
Unfortunately, my normal workflow is to use PuTTY Session Manager, and select "open with WinSCP" when I want to scp to/from servers, and Putty Session Manager uses whatever the default WinSCP settings happen to be (and I would not want to un-check "resolve symbolic links" by default). Putty Session Manager does not use WinSCP's site-specific configuration.
I am now reading about WinSCP's PuTTY integration, and the possibility of using WinSCP as my session manager for PuTTY. The difficulty there would be the exact opposite: getting WinSCP to use the site-specific configuration in PuTTY. According to the Integration With PuTTY
page, I can save PuTTY site settings with the same exact name as a WinSCP site, and WinSCP will then instruct PuTTY to open that session, using the configuration saved within PuTTY.
I will experiment with that today.