I dont remind where i saw that, in fact it’s even may be on the old udn docs for UDK. But the article was saying that its would be a good idea to use the server authority stuff from the network model even for single player since its harder to cheat and have other advantages since the client sends info while the server do all the logic stuff even of its in the same executable.
Does this still apply to UE4 or its doesnt worth the efforts?
Never make clients communicate directly, but rather route everything through the server and check it there.
If you let clients communicate directly to each other it’s very easy to spoof your health or location.
For some more information you can look at this page and other parts of the documentation on multiplayer. This stackexchange question also explains things more clearly.