Related to the closed MC-231561 when a player join to a server if the server its outdated show a message like the cliente its outdated and not the server also the messages for multiplayer.disconnect.outdated_client and 
multiplayer.disconnect.outdated_server are the same then in any case the message show is client outdated.
 
Replication:

• Run a server in 1.19.3 (can be any only need make sure the server is old than the client)
• Try to join using 1.20.4
• When join the server show outdated client and show to use the server version
   
  Notes:
  In NMS the check where decide what message use looks hardcoded to 1.16.x