I can guarantee you that it was a 1TB / 6G RAM model they used.
But keep in mind the file they were demoing...
150 layers, 9ft x 9ft, at least 300dpi (if not 600dpi), and a file size of over 3 gigs. Are you going to be doing anything that requires THAT kind of layer management? (My guess is "no") I've said this before: if you're working on a file like THAT, you're probably not working on it on the iPad.
I've also said this is a few threads now: Apple has 39 iPad Pro models between the 1st and 3rd gen versions released.
Six of the models have 2 gigs of RAM, the majority of iPP's (Twenty Six models!) run on 4 gigs of RAM, and Only FOUR run on 6 gigs of RAM.
You could say that Adobe is going to make Photoshop run on 6 gigs of RAM, but the majority of the user base will not have that. I would venture to say, based on price, that there's fewer 1TB models floating around than any previous models.
But the truth points to this: 4 gigs of RAM will suit you just fine for the next couple years. And, like always, Apple will release a version of the iPad that has better specs than the 2018 models, and we'll all be freaking out because the 1TB models will have 8 gigs of RAM while the rest have 6!
App creators will not ice out 35 versions of the iPad Pro just to make their programs run on 4 models.