It went through a re-design recently. I don't think I would call it a well-guarded secret though, if you look at Phabricator's Differential, it is very similar [0].
Reading through that page it seems like every single component is an unrelated, seemingly random, “cute” name. Are cli, triggers/actions, and rules too generic? Out of context, what meaning do Arcanist, Maniphest, or Herald have?
But yeah... even I find the names difficult to handle and remember, even after using Phabricator for more than 4 years now. Nevertheless, it is a great piece of software, especially the code review process is top-notch.
[0] https://www.phacility.com/phabricator/differential/