They do all right . . . .
I note I wasn’t particularly thinking of Harvard, since they are actually on the top 15 PhD to professor list. But it is certainly notable they are only 13th on that list (just after Maryland, and just before UCLA/Wisconsin). Whereas they are third on the Bachelors list, and Maryland, UCLA, and Wisconsin are not on that list at all.
Again, this is just underscoring that while the academic paths to being a professor in CS (and the vast majority of fields) tend to be concentrated into a relative few PhD programs, the paths to those PhD programs is less concentrated, meaning they go through more colleges.
And it is further underscoring that the colleges best for placement into those PhD programs are not necessarily the colleges of the universities with the best PhD programs. Harvard is on both lists, but much higher on the college list. Yale isn’t on the top PhDs list, but is on the top colleges list. Maryland, UCLA, and Wisconsin are on the top PhDs list, but not on the top colleges list. And so on.