By your definition, ANY ipad can do that, and thus can replace a PC.
But the question here is, how does the PRO replace the PC better than any of the lesser expensive ipads?? How can you make a case for people to buy the PRO over the regular ipad?
Any iPad can do that but the iPad pro can do it better. It's the same with smaller sized computers vs larger and more powerful computers. The larger or more powerful computers do tasks better.
I'm buying an iPad pro simply because of the larger display where I can fit full sized PDF files on screen or side by side with a note taking app or safari open. I sold my 15 inch MacBook Pro since I seemed to have less use for it every year.
I didn't store anything much on it, pictures were on my Mac but it's also in iCloud Photo Library, documents are in iCloud, music is purchased with Apple iTunes and now I use Apple Music, movies are bought from iTunes since I ran out of space for blu-rays and the quality is almost indistinguishable.
You guys are over estimating how much people use computers as their primary device and under estimating what they actually use the device for. A lot of people even use their cell phones or phablets as primary devices. A computer for many people just isn't necessary and a large tablet is more ideal for their life style.