I’m aware of that estimate. A 10.5 acre land does not sound like something at a “grand scale only Disney can deliver.” I’m not saying it can’t still be good, though.
In reference to a land, “grand scale only Disney can deliver” sounds to me like it’s implying a huge area, especially when in presented in conjunction with a piece of concept art that looks like a huge area.
That said, just as you noted about Pandora, the rockwork could plausibly be at “a grand scale only Disney can deliver,” especially with Zsolt Hormay at the helm. I don’t think there are other parks with such detailed/realistic rockwork at such scale as Pandora, Galaxy’s Edge, Cars Land, Mysterious Island, etc.