I suppose you could test your patch releases even if it's launch weekend, but having the ability to have a known-good version out of the box is nice.
Sounds like they shipped with 17.0.0, 17.0.1 was a day one patch and determined to be broken, but wasn't pulled before a fixed update was released.
In this situation, instead of being told not to update and you being able to skip the update and run initial setup on 17.0.0 if 17.0.2 hadn't shipped, they may have already updated the device to 17.0.1, and you would have had to wait. Presumably if it was bad enough, they might not sell you the thing until 17.0.2 was available for them to update it before you got it.
That said, in box upgrades are great to avoid huge patches when you open something that may have been sitting on the shelves for a while, and should help with logistics as well. Apple said they wanted to use more ocean freight rather than air freight for environmental reasons, and it will also likely reduce costs, but as another poster was saying, if you can't put the phones in the box until the final OS is ready, you can't ship the phones until the OS is ready, and ocean freight is slow. Being able to ship the phones and update them after they arrive in the destination at the destination store/distribution warehouse eliminates a pipeline bubble.