I saw many software engineers, with several different study paths, not knowing anything about how a computer and a network work. Apparently this doesn't affect significantly their efficiency at work but it's kind of stunning.

On the other side, I started from logic gates, registries, network packets and ended up with their same skills, with some 20 extra years at my disposal (I couldn't learn React before it came into existence but I know JavaScript since day 1.)

An exam on the second year of CS required us to write a simulator for a toy CPU, with the microcode to implement some simple machine code instructions. I remember the curses interface on a VT100 and the professor testing the program.

I wonder if I could have studied my books and those other books before I was 25. Why not? But I think that it's much harder to "know" software quality, software design, software testing, deployment, software life cycle than it is to learn the fundamentals. Anything that somewhat deals with people is messier and more difficult than something that deals only with machines.

That's like saying being a mathematician involves how well you can sell yourself, therefore marketing and networking are core skills in math. Marketing and networking are core skills of life no matter where you are.

Nope, as the OP said, you are misunderstanding that these books aren't teaching "soft skills", they aren't about networking or marketing, they are about how you collaborate in a work environment and build maintainable software that meets deadlines. If you haven't give some of them a shot, I find them a refreshing break from algorithms heavy books and get a lot of value from them.

It's not like that at all.

Software ENGINEERING skills are important for software engineers. Period.

Code are messages written for other coders so writing clean and readable code is a soft skill. Things like picking good variable names, designing the structure so things are easy to find, designing the architecture so the intent of the writer is apparent etc are all definitely soft skills.