I have to admit, as an old fashioned cruiser, I don't much care for this booking so far ahead malarkey!
I've just been looking at the options for our June cruise and it would appear that bookings for the 'included' options are only open until 6.30pm? I assume that if you want to dine later it will be a case of joining the virtual queue once onboard? I had an Olive Grove booking in my basket that got taken while I was looking at the rest of the options!