I, for one, think that they chose a circle just to be different and symbolic and nothing else.
A circular design is not very appropriate or efficient for any kind of building. If you look at the narrowness of the curved roofed area, the square footage they have there could probably be provided by a square of about 1/3 to 1/4 of that diameter (a square being one of the most efficient shapes in terms of usage and space utilization). That means also that the square would have 1/3 to 1/4 of circulation area. Than there is the question of all walls not being at right angles. All custom furniture. All custom glass.
This shape is also as un-green as it gets. Has about 10 times the exposed wall surface than a square which means 10 times cooling and heating loss. I am sure that they applied all kinds of green technology but imagine the savings using the same technologies on a square.
If it is the interior court yard they are after, there are rectangular court yard designs as well.
And, if it is symbolism (infinite loop!) they are after, that full-circular design should have included a "bite" out of the circle as they have it in their logo. That would mean a lot more "Apple" to me than this non-descript full circle. That bite would also create that special spatial condition for the main entry. As of now, I am just imagining somebody walking/driving around and around to find the main entry. Of course there will be roads and signs and such leading to the entry but that is just a bandage to cover up the situation that there is no visual point of main entry on this circle.
This generic full circle or ring does not say enough "Apple" to me.