While I agree with the 'what are they hiring for' sentiment, and have done a couple of the two-day interviews you described, I think the consensus is that SOME of the hoops candidates need to jump through are just that, hoops-to-jump-through.

When presented with 1000 applications of similarly (numerically and skills) qualified individuals, how a company chooses to differentiate varies. Some invite you in and throw you in the sim after the meet-and-greet, and some make you jump through a dozen, seemingly unrelated hoops. Those that want the job, jump through the hoops. I know I've jumped through many hoops in my career that made me scratch my head.

Advice to the prospective candidates: jump through the hoops, do your best to nail the bullseye on said hoops. Get your application reviewed by many, many eyes. Micro-check that thing for consistency: every 'I' dotted the same way, every abbreviation and capitalization done the same way throughout.

Get yourself psychologically ready for the interview in whatever way feels right. Listen to all the advice and use what makes sense to you. I know people who used several prep services and felt that every one added to their confidence. Others used prep services and didn't see the value. I also know people who went in with no professional prep and nailed the interview. You have to decide how much you need to be 'ready'.