It was that image that gave me the idea that they were thinking that a ballhead would be sufficient. And, of course, that has the advantage of more easily converting over to a normal head.
To be fair, without a head underneath the tripod needs to be perfectly leveled since the Gigapan head has no provision to level the horizon or set altitude. A leveling base would be a better option, of course, but adds to the total cost. And leveling the tripod itself can be done, it is just more work and time. Anyone that has shot panos without something like a PCL-1 or a leveling base understands this well
I think it would be interesting to play with that thing for a couple days, at various focal lengths, with and without a head underneath, to see how difficult it is to stabilize .
For sure though, the head they illustrate is not what I would put under that thing, although I can't ID it for sure from the small web images.