Solution: Take Ownership over pso2_bin and all of its files.
Before you ask, I DID undo the reddit fix where I copied pso2.exe into being pso2launcher.exe; by restoring the old pso2launcher.exe.
After the update however; I can't start the game now, like everyone else had. (I had zero issues before besides lobby lag, which I manually fixed by directly launching the game with the reddit fix.) I press start game on the launcher, nothing happens. No nProtect / GameGuard, no error messages, nothing. There's no PSO2 processes running invisibly either.
Check File did nothing to resolve the issue. It completed within 2 minutes, 35 seconds as I have an SSD as my only drive, thus extremely fast: