Of course, having one specification would mean you don't need to patch as often, so the X-Box games wouldn't need a patch, but I BET that you will be needing patches even if you just have to cope with a nominal hardware platform. Why? Because the coders involved are complete twats who think 'okay, I acn't get this to work, but no problem, I'll release a patch afterwards'. This is a bad attitude.
The idea (the one at least I have) about quality assurance, is checking every game to see fi it's arse or not. That's what Nintendo does, if a game sucks they don't want it i their console, do they? Letting everyone program for a machine can damage it.