It's crazy how disrespectful(and frankly insulting) these companies are to candidates, under the guise of trying to get the best. I would assume the best aren't sitting around on their hands for months waiting for offers, nor are they overly willing to be jerked around.
(Things are quite different for other not-so-sexy companies that need engineering talent.)
For those who decide to go for a FAANG job - maximize your time. Prepping for an interview at one, preps you for the others, with minor differences.
So try and set up interviews with them all around the same time, while you are well practiced. Throw in a few smaller companies somewhere in there too, with different interview styles. Schedule on-sites for your least-desired opportunities first, and consider them warm ups.
All the G engineers I work with have been there a while, so they went through different processes.
Yup, that's how I decode it as well.
But I do vote with my feet.
* Worked at Google until 2015. Culture might have changed a bit since then.
Having a long, drawn-out process will dissuade a lot of older workers with families who may not have time to invest in practicing for the interviews or scheduling them all, again maybe something Google benefits from if they want to have young workers who are more easily shaped and eager to devote more time to their jobs.
My domain is backend distributed system and FB arranged a front end manager to interview me and he explicitly said I was matched to his team, WTH?? then the interview feedback was I do not have their expected skillsets.
Why waste my' time & effort?