I would argue that the function works as designed. It is correct if the country and region is taken from gc.com database. The problem is that caches not located i
The filter is not for caches located in a country like written in the QA you linked to
"None of the nothernmost, southernmost etc. caches is located in Germany."
"A map showing the most North/East/South/West and oldest geocaches of a selected area. Use the loop filter to choose how many geocaches you want to show for each criteria."
With the definition that country and region is as set on gc.com.
There is not border polygons for countries on pgc. And the county polygons often dont go out to se like in New South Wales
There is no easy way to auto detect if a cache is inside a county.
And you will have defenintion problem with how large part of the sea is part of a county.
And all countries does not have regions and counties defines
An option would be to add a filter to required the county to be set on the caches.
There is an fix if you are a paying member. Just add loops until all cachesw are inside the country according to you definition. Loop 7 is enough for germany