I’m not quite sure what the question is, but no, tickets aren’t held back- anyone wanting to go needs to call, buy online, or buy in person before the event, whatever it is, sells out. The only exception I know of is for those with a military id. They can buy tickets to Halloween and Christmas parties in person to sold out dates, regardless of whether it’s a military discounted date. I assume this is a friendly (and well-deserved) concession due to the sometimes unpredictable schedule of our military members.
That's a good example! Disney never sells out of either tickets or rooms. You might call Disney to book a room and be told they are sold out. While it's true that Disney no longer has available rooms, other vendors (i.e. various travel agencies) will have rooms and tickets. You just have to know where to look. Disney sells huge chunks of rooms and tickets to a large assortment of travel agencies. Also, in Florida, Publix, Winn Dixie, Wawa and Target all sell Disney World tickets.