NDAs.
That's my point, really. FAANG employs a ridiculous number of SW folks for outliers to be quite expected. As a reminder, we had Snowden in NSA who at that time was estimated to have a headcount of 20k or so.
Snowden's revelations are infinitely more important to the public interest than some recommendation algorithms, as evidenced by the fact that he had to leave the country and seek permanent political asylum. He didn't do it for fun.
That or all the employees who work on the core algorithm are sworn to secrecy in a blood rite cabal with embedded cranial explosive traps if they ever speak or write anything outside of corporate SCIF’s.