Long story short, the mod seems to be very nonfunctional these days, either being unable to populate the list of filtered tiles (highlighting still works) or returning 0 results even when it shows that there would be >6k matches. It also breaks if you try to run it without the biome check enabled for worlds above 50% size, and Impassable toggle must be reset every time you start a new world and try to filter
Most of this is chronicled in the steam workshop page's comments probably, just thought I'd bring it up here