"Allow Server Listings" option is briefly ignored

The client does not send the packet (ServerboundClientInformationPacket) needed to receive this information until a little later after player login, which can cause a condition where despite a player having a disabled listing, they are able to be seen for a brief moment. 

The proper solution to this is to perhaps include client settings as part of the login process, in order to ensure that this information is sent early enough.

A temporary fix was included via Paper that will simply mark them as anonymous until the packet is received. Paper/0975-Disable-allowListing-before-received-from-client.patch at c004436e077e8279c2ab567f8fc60682627815c2 · PaperMC/Paper · GitHub