Setting fullscreen resolution while playing in Windowed Mode

When launching/playing a game in windowed mode, the lower resolution settings remain when using the command "r.setRes 1920x1080f."

The user is saying for example if he runs the command "r.setRes 640x480w" and then tries to use the "r.setRes 1920x1080f" the original resolution is kept and it goes to fullscreen.

The expected is for it to scale fullscreen with the given resolution of 1920x1080. Keep in mind I was not able to reproduce this issue, but the user insists it is a consistent problem.

User provided steps to follow.
Was able to reproduce 0/5 times.

1. Launch a standalone game (or a packaged game)
2. Type in the console: r.SetRes 640x480w: it works well, the window becomes very small.
3. Now type: r.SetRes 1920x1080f: you go full screen, but the resolution remains 640x480, resulting in a blurry and pixelated screen.