Q: Are sold out breeds ever included in a hatchery choice assortment?
A: Breeds that are not available individually may still be used to fulfill assortments, since the assortments consist of breeds that have hatched better than we predicted on a given hatch day. In other words, assortments can certainly be (and often are) fulfilled with otherwise sold out breeds, because once we've provided for the orders reserved for that week, we can use the remaining birds for assortments.
This is a function of having to literally count our chickens before they've hatched: when making our availability estimates, we are conservative so we can avoid disappointing anyone who has reserved a specific breed. This is why assortments may be available even when the individual breeds have already been spoken for in advance and are sold out for the season.
All that said, if you want a specific breed or color, you'll want to order it separately, because the assortments are hatchery choice. YOu don't get to choose which breeds or colors you receive in an assortment.