The 990 doesn't do any video processing to the component inputs. On the other hand, VGA and component are not interchangeable signal formats, so using component switching to switch a VGA source is not likely to work - whether that component switch is the 990's, some other receiver or processor's, or a standalone component switch.

I believe the reason that the component to VGA cable works is that your projector's VGA input is doing double duty as both a VGA and a component input.