Smart move, keep patient count conservative whenever possible
It was a very shrewd move to announce they have qualified about 250-300 patients on a named basis. They need to keep outward exposure focused on how small the patient population is to maintain pricing strength.
If they laid claim to 6,000 patients then regulators and insurers would try to drive down the price of treatment. By keeping the number small, they have a strongly defendable case to maintain pricing strength, then as the patient population grows substantially beyond the pre-registered 300 to more than 3,000 they get substantially higher revenues and beat all estimates.
Certainly if they laid claim to 6,000 patients and only sold to 3,000 then they would be viewed as having missed their target.
I do have to laugh because this initial patient found of 300 named patients is like pre-orders on the first Xbox or iPhone. It is tiny compared to the full sales amount once it starts selling.
For me, I'm glad to know they already have 300 patients lined up as that is already $90M targeted. That resets the bottom rung of expectations and raises the floor substantially, which should lead to a strong product launch which will then snowball.