Since not every car they sell is capable of it, I'm guessing this means to demo it for everyone who ordered it (or ordered a car capable of it, since the subscription can only be enabled on such cars).
The delivery process takes like a handful of minutes, and everyone who orders one still has to go through it, so if they're mandating a drive, I guess that roughly doubled the delivery process time.
Ah, I wasn't aware that new ones came "FSD Capable" by default.