In the “Multiplayer in Blueprints” section of docs.unrealengine.com, under Gameplay framework review. It states
“To add multiplayer functionality to your game, it’s important to understand the roles of the major gameplay classes”
Gameinstance is the very first thing listed, but is not mentioned for the entire rest of the page.
Should read something like
“The GameInstance exists on the server as well as the client, but with no replication. The Client and Server have their own distinct GameInstances and cannot communicate between each other. GameInstance is an excellent place to store persistent variables and anything that needs to survive through level changes as it is the only gameplay class that survives through level changes.”