I've seen many variants of the recruiting process from the cute product feature disguised as a take-home to 6 stage interviews with two engineering(!!) interviewers per round that cost the company a few thousand per (un)successful candidate in man-hours.

Which is hilarious in an industry that is pretty binary ("you can build it") || ("you can't build it"). Doubly so when the majority of dev jobs are in web which is easily explored in the candidate's language of choice with basic CRUD / RESTful concepts.

Of course there is. You can generate studies that show roughly anything.

It may not be the majority, but if the research is all done in-house by various firms, there's no way for anyone to know that.

By research I mean of course properly done research.