Google's and Mozilla's geolocation services make a best effort attempt to not store information about WiFi APs with a "_nomap" SSID suffix.
"_nomap" APs can only be filtered on the client-side because requests sent to servers do not include SSIDs so server can't determine which AP measurements in the request to ignore.
"_nomap" APs should be omitted from both requests to geolocating services and submission (observation collection) services because servers commonly store AP information from both types of requests.
Fixed in git master (though I didn't get to really test it). Thanks.