I'm really happy to see that they're canceling all open orders. It's much better than letting them stick around and then execute with unexpected behavior. It looks like NYSE learned from what happened related the FB opening (just as you alluded to), and what happened with Knight around the same time. Playing it safe can be a smart move, even in the stock market.
My immediate reaction is that their system shouldn't require canceling all open orders. But I admit that I don't know much about matching engines.
If they roll out a new version of the module that creates orders, I would think it makes sense to include the version of this order module in the order data structure. This way they can delete only the bad orders, created by the faulty module version, instead of all open orders. But it's also possible that I'm way in over my head here :).
