I've been buying these type of collectible figures for years, from various manufacturers including Square-Enix, and while the legalese conveys they're completely random, that's because the purchase of a random individual box, does not guarantee any particular figure, and could be the secret.
However, what you're pre-ordering and buying from the S-E store is essentially a display box. A box that would be displayed at a retail establishment that would allow the purchasing of these boxes, individually. That's why they're individually blinded boxed, even when sold by the display box.
The retail box, or case, contains a set. A set of figures that make up the main set, which in this case, are the 7 characters. However, there's an 8th individual box that could potentially be the secret figure, or a duplicate.
Someone going into a store and purchasing these figures one by one, would have no guarantee or knowledge of what the potential figure would be. Buying the entire case or display box however gives you the main set. And maybe the chase.
This is why on the secondary market they're all relatively the same price, however Crossdress Cloud is exorbitantly priced. Because they're are less of that figure than the rest. It's scarce. But the others? They're all in a box.
You're gonna get a case and open them up to find 5 Aeriths and 1 Barret. That's not how it works because then no one would buy the cases, stores or individuals. They have to maintain a variety for individual buyers so that they will buy up a box, and chase the secret.
