What industry has four rounds and a 3.5 hour interview session? To me, that wreaks of incompetence. Unless you're going to be the VP of something that's just inconsiderate and wasteful. Even a senior dev position should take at most two hour sessions and a 30-min code practical.

My guess is it was some HR person's whole job to "enhance hiring practices" and this is what they came up with. Probably got a promotion out of it for the great work they did. And they'll probably get another one when they "streamline an inefficient hiring process" next year.