Technically those are not floor standers as it's really a subwoofer pedestal (PedWoofers) and speaker that are sold as separate units.

Similar to Monster's high end speakers on the sub pedestals.

When I think floorstanding speaker, I think of a speaker that is sold as one unit that sits on the floor and does not need stands or wall mounts to project sound to the proper listening position.

I don't think you will find a single THX speaker that is a true floorstander.

At least not for the Ultra specs. As the requirements for controlled vertical directivity are relaxed for the Select spec, you would be more likely to see Select floorstanders.

As I'm sure that any THX Ultra speaker manufacturer must assume that their speakers may be used behind a screen, a one piece true floorstanding design just isn't an option.