I've tried it out. It's quite obvious the limited number of crawled sites when searching for anything obscure or one step outside of programming.

Even 'javascript reverse string', which I expected some docs or stack overflow pages seems to give me a HN thread, someone's github repo and a not very related SO thread.

Is MDN, MDSN, more dev docs documentation on the roadmap?

It's definitely an interesting technique. Do you have anything in place to detect garbage, substenceless articles like which has started popping up on Google?

I've seen the occasional one using github repositories or pages. Looking at the current list you're broadly reliant on moderators and communities, and as the search engine you moderate which sites are indexed.