I didn’t say it was unique and it certainly isn’t, I’m sure, if you go look at every other hotel in the world. The style is subtle, modern and I feel like the differences are in the details and the artwork. I’m presuming their vision was as though it were a modern Riviera hotel, but as you say it takes in other influences also. It isn’t entirely architecturally based on Walt’s travels, but much of that is in the artwork and artefacts that are placed around the grounds, that do for the most part follow specific artistic movements.
It definitely isn’t the same as any of the other Disney resorts, so it offers something different for Disney/DVC guests.
I will add, that these are my opinions and not going off what Disney has said. So if I’ve said it’s not Art Deco, it’s because I don’t think it is. Others may disagree.