[Boldened15]

Detection algorithms can be less useful in general if they're public and open source, eg. website operators sometimes mass ban on a delay so they can trap a lot of misbehaving users and don't immediately tip off the suspicious behavior.

Although in this case it's already a publicly available extension so even without the algorithm details you could easily check your text against the detector and tune it until it passes... but maybe having the method be public would make it easier for users to prompt engineer the AI to write in ways that wouldn't be caught by it.