Granted, I never worked in SEO directly.
I'm still not sure what the truth is. You raise a good point.
Google introduced nofollow in 2005 to either let people help fill a gaping hole in Google's tech at the time or for the smart marketing move of making people fixate on their magic attribute. Both under the guise that spammers would care.
It's been twelve years.
The SEO advice industry and Matt Cutts' blog these days are probably like when I try to ponder why my cat scoots its waterdish around the room before it drinks: attempting to find backsplanations for the idiosyncrasies of a neural network that nobody quite understands.
That said, Google probably has some heuristic for considering them. It probably errs on the side of ignoring, but it would be stupid for Google to ignore all nofollow links. Even more so because spammers don't like them.