These aren't "algorithms" in the traditional sense of that word. They are complex, convoluted systems with hundreds of moving parts/services owned by dozens to hundreds of teams. There's no one individual who has a total understanding of the whole thing, and only a few that could speak to it at a high level. Most folks are busy optimizing and improving the microservices their team owns and such. The few folks with the high-level understanding are typically senior enough where divulging this info is neither particularly thrilling nor worth any potential risk.

And yes, recommendation engines are not nearly as exciting as the conspiracy theories around them.