The interview process is one of where the "sunken time fallacy" is at play.
1 - 30 min interview.
1 - Panel Interview.
Wait 2 weeks.
Reach out for an update.
1 - Project (best to copyright or secure it in some way against theft).
1 - 4.5 hour interview consisting of endless panels, a tour of the grounds (in an effort to distract from what is otherwise an unnecessarily long and arduous process).
Then they leave you on read indefinitely.
Also you'll want to check the job description after this interview, you'll find they have updated the description to match their latest candidates experience. As of to say, they want what the candidate has to offer but not the candidate...as they won't fit in with the culture. (I encourage you to check the website for very evident "culture").
If you're the type to be in it for the long haul, this may be great for you! For the vast majority of the rest of us who would like a more efficient hiring process, you'll more than likely see this for the farse it is and move on. I suggest the latter.