There's also the issue of distance for a mouse cursor to travel to select something. I think the general issue is imposing one interface for every mode of input instead of options, so either select an appropriate interface depending on how the start menu was invoked (even if it's just scaling it down to a confined space) or letting people select the default however it's invoked. Yes that's going to be more work, but when we're talking about the largest corporations on the planet I struggle to believe they can't afford it.