http://maldomapyy5d5wn7l36mkragw3nk2fgab6tycbjlpsruch7kdninhhid.onion
Remote nodes constantly ask other nodes what block height is the highest they know about, to decide who to download which blocks from. Spy nodes use that data to see if a node is fully synced or not, because only fully synced nodes can send transactions. They are managing their own resources effectively by not making lots of connections to nodes which are not fully synced.