After playing around with the Teams 2.1 client a little more, I think I see the problem. The filters option appears to indicate that No filters are chosen, but if you go to settings (cog wheel)

Settings

You can see the options to control the brightness and soft-focus filters.

Video filters

I think this is because the soft focus and brightness filters are deemed to be basic video settings whereas filters are now more like the Maybelline set (https://office365itpros.com/2023/07/24/maybelline-video-filters/) which are loaded by an app and can therefore be blocked by tenant administrators.