Isn't this exactly what Apple did with the M1 chips when they were first being released? Plus, Apple announced they would do developer kit applications for the Vision Pro at the same time they announced the Vision Pro, so they couldn't have based this decision on the traction with third party developers.
It is exactly what Apple did with the M1 chips. I had a developer kit Mac Mini with an M1 chip in it that I sent back to Apple when the developer period was over.
This is Apple, they have billions in cash on hand. There's very little pressure to make money on the first gen Vision Pro, not if they're committed to the product line long term.
Anyway, it's been reported that manufacturing these has been a slow process, hence the slow rollout. They don't expect to sell a ton, not at $3500.