Incompetent is what it is. The PC, particularly Direct X have calls that set internal and external resolution. You set it what you want it to be, and that's it. External DLL's can intercept these calls of course, but normally that's never needed, because there is no realistic way any developer HARDCODES resolutions in a PC game. The internal/external resolution is usually read by variable (from game settings) or Desktop Resolution.
So basically, they hardcoded the internal resolution instead of making a variable linked to the game options despite them having made a variable to set the external resolution (Which goes against anything DX API tells you). You have to do that by choice, it doesn't happen accidentally.