Bloomberg's Mark Gurman outlines early details of Apple's plans to release the Vision Pro AR headset. Availability for the $3,500 device will be limited upon its launch...
I think it's just worded that way. They've discussed it as an add-on in other places.
I'd read it more as "maybe they have you try on the headset as part of the fitting process" and it won't work for you without the correct inserts on hand. Or maybe just that because you need the inserts to use the device, they want to be sure they have them on hand if you end up having to book significantly in advance so you aren't wasting your time and an appointment slot.
I've used HTC Vive, Valve Index, Sony PSVR1 & 2 as a glasses wearer.... It's definitely doable but the inserts make the experience a lot nicer. The current VR lens insert market is around $50-100 depending on the vendor and your prescription strength. I'm guessing Apple will charge similarly for theirs.
They might just be using it to get your IPD. Then they'll ship the device with a non-adjustable IPD. I feel like they'll make you buy the inserts separately.