I just checked Apple stores and Best Buys in my area online. There area lot of new Pros in stock in both sizes.
Based on this, I tend to agree that demand is not what Apple hoped for. Or maybe they did expect this and just decided to maximize profit margin over quantity sold. Who knows. But a completely redesigned iPad being available everywhere only one week after release is not a sign of blockbuster sales. It's just not.
That doesn't mean it's a flop, but it seems more like a "reset" in the direction that iPads will take in the marketplace.
What I do know is that this is exactly the kind of iPad I always wanted, but here I am holding off. I might not get this model at all. I'm usually ok treating myself to nice things, but the new iPad is just really really expensive, and my 9.7 Pro has lost a whole lot of value since I bought it. Not to mention that it's still a very capable device.
The other problem is that, while I can do a lot of things on an iPad, I cannot do everything I need to on it. I still have to turn to my work PC or my Macbook at home to complete a fair number of the tasks I do. The iPad is getting more capable all the time, and it's getting closer every year to being a full laptop replacement, but there are still quite a few tasks I do that are either way more efficient on a PC with a keyboard, mouse, app windows, and a full file system, or just impossible to do on an iPad.
If I bought a new iPad with keyboard and pencil, and sold my old one on eBay, I'd still be spending a net of over $1k. That is a lot of dough for a tablet that serves as a third device.
If you do frequent creative work or use your iPad as your primary computing device, then it makes a whole lot more sense. But that's not me. Which is a bummer, because this new iPad looks amazing.