It does not change the pre-rendered cutscenes. Those remain in 4:3 with letterboxing, but this is a minor concession.
(like 640x480). dgVoodoo will intercept this and upscale it to your chosen HD resolution. If the game is still in a window, press Alt + Enter to force fullscreen. ⚠️ Known Issues & Fixes Fix Frequent Crashes (Single Core) chaos legion pc widescreen fix