> What I wonder about this idea - it sounds like they started out with a open house for everyone who applied, regardless of qualifications, instead of phone screens. So how many really qualified candidates are going to be interested in travelling out to the company for an "open house" with everyone else who applied for the job?

Probably not many, but as was discussed recently in the context of TripleByte[1] some qualified people have "bad" resumes and may struggle to get phone screens. Go through enough resume-level rejections and you might welcome such an open house, if for no other reason than to network with people you might not otherwise be able to meet.

[1] https://news.ycombinator.com/item?id=9507089