thanks @rachelda !
I've played a bit more now and changed the feed type from domain to URL, but I'm still getting very inconsistent results. You can see two examples below:
block2,bite.lv,URL,high,high,AB,ISEC
block3,disk.yandex.com,URL,high,high,AB,ISEC
1) bite.lv gave me AB userchek block page very first time, but later DNS started being blocked and blank response in browser. Could be it will generate block message only once per session
2) yandex case just gave me blank page = DNS was blocked.
Screenshot shows difference between two cases - first one generated log for both - DNS and URL reputation. The second only DNS. Even though both are defined as URL feeds.