Filtering results on the map is a preview feature, that means, for lower zoom levels we may omit some results.
Let us know, if you liked to see proper filtering in all zoom levels. Currently the data is so sparse, it is probably ok like this.
Techinicaly, the issue is, that below zoom level 10, we load our climbing map tiles which show POIs only each ~ 1km. So if there are multiple crags/areas in this section, only the one which has the most routes is sent from the server. For displaying all results, it usually shows the "climbing=area" which is correct. But to do proper filtering, we would need to send every crag+area, which is technically impossible.
Below zoom 7, the distance is 80km. (See code here)
Introduced in https://github.com/zbycz/osmapp/pull/1425