Matt Hauger, with a theory on why devices like the AirPods Pro are available for pre-order immediately:
I wonder: how did Apple decide that these devices would be available for preorder immediately? Why not a few days later, as with the new iPhones? Here’s a cynical theory: maybe less expensive items (like the AirPods or the Watch) are more likely to be impulse buys. The customer doesn’t get a chance to weigh her purchase carefully. Instead, she acquiesces to the lizard-brain desire that Apple’s marketing engenders.
I would guess that Apple primarily decides when devices are available to pre-order based on their expected demand and how many units they’ll actually have on the ship date. But I wouldn’t be surprised if the idea of impulse buying comes into the conversation at some point. I mean, they do need to actually sell these products after all.