Most of the assumptions in Tiebout's model are purely theoretical. That is to say, they exist purely at the level of theory rather than practice. For instance, it may be theoretically sound to argue, as Tiebout does, that consumer voters have perfect knowledge.
But as with its economic counterpart, the assumption of perfect knowledge is simply not borne out by experience. Hardly anyone, if ever, has the kind of perfect knowledge with which to make economic or political decisions such as relocating so as to maximize utility. And for many people, upping sticks to go and live in another community is much easier said than done.
And so most of the assumptions in Tiebout's model generate, in turn, an extreme model, a theoretical construct that is far removed from what really happens in the world of lived experience.