Helper baseclass sets `this.opts` in `setConfig`, not `this.config`?

I was trying to work out why the documented details around `Scenario(...).config('SomeHelper', {...})` weren't working for me, and as
far as I can tell, the default base class implementation of `_setConfig` is actually setting `this.opts` rather than `this.config` (which I presume is the correct version, since it's mentioned both in the docs and is assigned initially in the constructor).

https://github.com/codeceptjs/helper/blob/master/helper.js#L48

Unless I'm misunderstanding something here, I'd expect _setConfig to also be updating `config` member?