Like it says on the tin, I was able to get Titanfall 2 to run properly in 4k through Origin by editing the videoconfig.txt file in Documents/Respawn/Titanfall 2/Local and it looked great. However, after getting the game on Steam (I'm always happy to support Respawn and the Titanfall franchise) I discovered that the 4k fix doesn't work. The videoconfig.txt file keeps resetting to default values or the game simply ignores it when active.
I can't tell if this is an issue with Steam replacing local files with cloud files or if the Steam version of the game keeps a conflicting videoconfig somewhere else. This isn't a game-breaking issue, but it's an incredibly annoying and noticeable one.