Which... is fine! They're allowed to open source solutions for problems that are unique to their massively scaled architecture! Others can learn from it -- even if others don't have the same problem.
It is worth keeping in mind that very, very, very few people/companies are required to solve the same problems a company like Meta is.
It is worth keeping in mind that very, very, very few people/companies are required to solve the same problems a company like Meta is.