Firstly, there's no such thing as a Pro device. Anything can be for professional use.
Agreed, but Apple choose to market it this way.
Secondly, most people are very, very gullible and will believe everything they are told. No one with an ounce of intelligence should have the expectation that Photoshop on iPad will make their PC/Mac redundant. At the same time, people who make their living using Adobe software may find that Photoshop on iPad serves a purpose. For the average Joe, not so much.
It's all about options. Having the option to make some changes on the iPad while travelling, at a coffee shop or simply relaxing on the couch is great but only if the experience is worth it. No one is saying these devices are to replace a full workstation even though in theory they could. I actually edit complex images on my Pro at home instead of my Mac and for the majority of tasks it is at least as quick. The one time it really struggled was doing a very large panoramic merge with a number of RAW images and took a long time to complete. The internal filesize was in excess of 4GB so clearly having to swap to complete the task. I'm not a pro photographer, just an enthusiast but still hitting the limit of RAM.
Thirdly, there's no point packing the iPad with 16/32GB RAM & charging another $500 for something only a tiny percentage of people may actually use. I'm sure Adobe will optimise Photoshop for mobile use and scale the app so it works across a broad range of iPads, old & new.
I agree, but again it is like the storage options. Apple offer 4 choices - 1TB is one of them which is great but I don't require it so won't be buying it. If they could even offer 2 choices of RAM - 4GB & 8GB and charge accordingly then it gives the consumer more choice. Leave the non pro devices at 2GB if they so wish. They do this for the Macbook range and by their own admission, Apple sell way more iPads than Macbooks!
Adobe can also optimise their app all they want but you still can't cheat physics. If you pull in multiple RAW images as layers, you can't just reduce their memory footprint without impacting the end result. That is why a lot of developers place a limit on the number of layers you can use to avoid any low memory issues. Other devs allow you to create as many layers as you like up until available RAM is exhausted.