SetForceDisableSplitscreen does not appear to be working

SetForceDisableSplitscreen does not appear to be doing anything? I set it up like this in my game mode on beginplay, but when i call addlocalplayer, that player still gets there second screen. Im just looking to disable it for a main menu screen/cutscenes and turn it back on for the rest of the game.

if (UGameViewportClient* VP = GetWorld()->GetGameViewport())
{
VP->SetForceDisableSplitscreen(true);
VP->UpdateActiveSplitscreenType();
}

I cannot remove all players but 1 to accomplish this as each player need the ability to customize their character before the game begins.