No kidding. When I hear about long grueling hiring processes like this, I wonder what the hiring company is finding out in the 8th hour of interviews that they didn't in the 7th. Or in the case of one job my sister applied to: the 8th interview!
In this case, maybe that one person, at the end of a long day, who didn't feel the spark?
I wonder how much of interview overhead it would be for Sr Enggrs and Managers. Multiple rounds of interviews like this is overkill.