Totally agree with your points, but Epic is not involved with the Quake franchise. First one was by id, newest games published by Bethesda.

You may be thinking of Unreal I and II and Unreal tournament which were originally competitors to Quake II etc.

That's not the only reason we feel sleepy though.

Research is a little mixed, but it looks like the brain specifically doesn't get less oxygen during digestion. Your brain does coordinate signals telling you to slow down though.

Digesting food takes a lot of energy. Your body literally changes where blood is flowing after you eat to send more to your digestive system. That means there is less blood for other things like your muscles.

Your body tells you to slow down.