[yummyfajitas]

Requiring employees to work at a particular job site is uncontroversial; in fact, it's overwhelmingly the norm for all employment.

I don't understand - what does the "norm" have to do with anything? Are you asserting that some underlying legal principle demands that all employers stay within spitting distance of the average?

If not, I don't see how this policy would even fall within some sort of disparate impact theory. As far as I know, disparate impact lawsuits apply to selection processes. I.e. if the employer hires fewer members of a protected class, a process is bad. But if fewer members of a protected class accept job offers, that doesn't fit into disparate impact.