Check it out for yourself. Make a third person template in C++ and set the number of networked players to 2+. You can do it via dedicated server or listen server. The first player to connect will not be able to possess their pawn properly.
Interestingly enough, ONLY the C++ version is broken. The Blueprint Third Person Template works fine. The vehicle templates also work fine in Blueprints or C++. Was there a change to networking from 4.11 onwards in C++ projects that I wasn’t aware about?