This is wildly incorrect.
He talks about placing down BUILDINGS in an instance. That's pretty much it. However he spends a long segment talking about how island sanctuary is a "rank above" current systems like housing, gardening, and decor. These are not the same levels of content. Island sanctuary is an entirely new experience that expands upon the basis of currently founded systems.
There was also an interview prior where he directly talks about this overlap with housing:
Q: "With Ishgardian housing coming as well as the Island Sanctuary, players are wondering what will the overlap be, if any, between Housing/Estate activities and Island Sanctuary ones?"
A: "I won’t say there is no overlap in the gameplay, but they are fundamentally two separate pieces of content. If anything, we plan to incorporate many things that you can’t do within the housing/estate system into the Island Sanctuary. We’ll have more details down the road, so please stay tuned for further updates on this."
Basically, yes there's going to be overlaps. But no, this is not instanced housing.