Having your own tests of skills relevant to the job is different from relying on high school standardized tests.
That suggests that employers do not really believe what many say here about elite colleges, which is that even “hooked” admits are highly qualified at least to the “average excellent” level (including, but not limited to, test scores).
Also, do they note the difference between heavy core curriculum / general education colleges like MIT versus open curriculum colleges like Brown or Amherst, for this purpose when deciding whether a college degree indicates sufficient math or verbal ability?
That may also cause a selection effect in favor of those who had advantages while in high school (e.g. more access to test preparation), and against those who took non-traditional paths (transfer) who may have no or poor high school standardized test scores. But perhaps that is the intent.