That’s a rather serious conditional that I believes renders your point moot. The truth is that most law schools are not top-ranked law schools and therefore do not draw a large number of applicants with top-tier stats from top-tier undergrad programs in the first place. Let’s face it: If you’re Wayne Street University Law School - which I select because it is ranked #100 in the latest USNews and is therefore representative of an ‘average’ law school - you’re not going to receive many high-stat applicants from top-tier schools. Of those that you do receive and then admit, many (probably most) won’t actually accept your offer of admission, but instead will turn you down for a higher-ranked law school to which they were admitted.
The same holds true even if you’re one of the top-ranked law schools. While Georgetown Law is surely well established as a premiere law school, the fact is that many top-stat applicants from top undergrad programs who are admitted to Georgetown Law won’t actually come for they would rather attend another law school that is ranked even higher. {Georgetown also happens to have the 2nd largest student enrollment of any law school, which only compounds the problem of filling all of those seats with top-stat applicants from top undergrad programs.}
The upshot is that the overwhelming majority of law schools simply do not have the luxury of fillingl their seats entirely with top-stat applicants from top-tier undergrad programs. Choosing between an applicant from a top-tier undergrad program with middling stats vs. one from a low-tier program with strong stats is indeed a choice that they perennially face.