Is this assumed or is there public info about their algorithm?

In the first song of my Discover Weekly, if I google the very unique artist name, I get exactly four hits: their bandcamp page, their website, their Spotify page, and their YouTube channel that hasn't been updated in a 9 months, with that last video having 120k views. The rest is unrelated to them.

This doesn't refutes what you're saying, but I would have exactly 0 chance of finding them on my own, with the effort they're putting in.