I think "do the work of hundreds" is a little bit generous. It does save a little time, but does it really save so much time as to boost productivity 100x?
Most teams eventually need to on board new people, though.
Besides that, building teams of generalists is far easier if it's easy to dive into new code bases. Even with small teams highly specialized on individual projects, there are lots of advantages to having people be comfortable digging into other teams' code, which is much easier if it's more discoverable.
Making code that passes the grep test allows many more programmers who are vaguely familiar with the codebase to make changes.
Making code that fails the grep test allows a team of a few highly skilled developers who know the codebase inside and out to do the work of hundreds.
It's like mathematical notation, you generally need experience in that sub-branch of mathematics to understand the notation.