How do we know we are scanning a correct range, I mean what if someone scans all 588 ranges and finds nothing? You see, searching for addresses is a blind search no guarantee to land on the target unless you search the entire original range one by one.
There's a phrase in Chinese sounds like this "There are no cookies fall from the sky".
If someone can scan 48 bits in an hour, let's assume the key is in the 588 range, this means he just need 24.5 days to completely scan all 588 ranges. If he is so confident with those range, nobody will want to share such high probability ranges. It is a zero risk while he get 40+% if he share it because whoever find it need give him that. If the key wasn't there, he has nothing to lose. The final conclusion is he has no confident at all on those 588 range.