The parity clause will have the opposite effect, instead of developers releasing day one and delaying other platform releases, it will just piss people off and some wont bother at all.
Microsoft need to incentivise parity - store promotions, tools (like free unity and dev kits which they are doing), assistance, good relationships etc not force it.
Microsoft are leaving money on the table by not getting every game they can on the platform, they arent the ones making the investment in the game, I really dont see what difference it makes to them financially except for not getting more money from their userbase. Not to mention whats the point in shipping dev kits to developers who then cant use them to release games on the platform?
I can understand the business point of view of not getting games second, but really its only going to hurt them long-term.