As far as I can recall (and I am too lazy to look it up) the MOC orders on NYSE are guaranteed. I think it's done to make the world more confusing, but the general idea is that big board stock have more liquidity and thus the exchange can get away with guaranteed execution.
I didn't keep the whole record so can't tell exactly. My system ensures orders are placed at least 10 seconds before any cut-off times depending on the venue which would be 5 minutes for Nasdaq MOC, and the trigger for this particular order actually fired much earlier. But I don't rule out my own bug of course.
It looks like the order was accepted at the exchange though, otherwise it would not fill even partially, no?
I believe if you somehow missed the deadline it will still fulfill the MOC (if there are takers) but not guaranteed at the official cross. Experienced that many years back but never ever since then.
