Up-on querying servers, my development team have found that dedicated servers randomly (for no apparent reason) fail to send SetGameTags.
As shown here:
https://community.bistudio.com/wiki/STEAMWORKSquery#SetGameTags_in_detail
Packet sequence is normally blank for empty servers, so we interpret that for the player count.
However it seems that SetGameTags get pushed to sequence 11 when the server is empty on query.
I've attached several outputs
PacketIncorrect.dat
PacketOK.dat
Packet-emptyserver.dat
These should be self explanatory.
Segment delimiter is 0x00, first 6/7 bytes are to be ignored.