However, chances are they are the Bluetooth headphones Apple makes the most money on, and that early adopters of the new iPhone are the most likely to buy them.
Inducing (extra) demand for Bluetooth headphones and then leaving the market for such headphones to others in a period where your most 'able and willing to spend' customers enter your shop isn't the best of ideas.
(1) (nitpicking) it wouldn't completely surprise me if they were, though, because Apple has exactly one product, whereas its competition tends to create zillions of 'different' products.
I personally got conductive wireless headphones and really like them. Not Apple, of course.
Conductive is the future I think, I'm never sticking anything in my ear again.
[0] https://9to5mac.com/2016/09/12/apple-w1-chip-how-it-works/
Alternatively, the space was set apart as a hedge against the AirPods not being ready at he time of the launch of the iPhone 7 (yes, they were late, but not _that_ late. Presumably (again) they knew they could make them when they made the decision to remove the headphone from the iPhone 7)