Information given in this thread is not correct to my knowledge, all available seating ( bar a small percentage to cover late concierge bookings), is available to book, from the cruise release day. Blocks are not kept back or released , in a balanced way MAIN/LATE and I have never seen that even suggested before.
A small amount is kept for concierge who will get thier request if main or late whenever they book, that's it.
When Main is sold out, it's sold out, what people booking may see is that cruisers do cancel, and move reservations on, this typically occurs near paid in full date, thus may give an impression of a new release, but it's people who had main no longer going and thier reservations released back.
It's not block by block in equal amounts, really unsure where that idea gas ever come from.
If you wait list, it is looked at but not pro activally, so call
DCL every so often, around PIF date is good.
Restaurant managers have the lists uploaded three date before a cruise, they allocate them then, they can move some tables around, so can at times squeeze a bit more in in main if thry need, Main is most popular with young families, late with adults only if adults with high teen children who eat at 8pm at home.