In every classic book, you'll have lines that modern engines do not like. I stumbled on the very position when I read the book, and I remember the phrase "dead meat" being extremely cryptic to me.
However, I found, that Silman's books are much better than, say, Chernev's Logical Chess Move by Move (which I stopped reading precisely because of the bad objective quality).
It is very good that you check everything with an engine, that you do not understand. However, even if a modern engine considers a variation better than Silman, it is still very valuable to read and understand Silman's annotations, because you'll learn something about practical "human" moves and how to generally think about positions, even if concretely, a certain other variation might work slightly better. Often, these better variations are hard to assess for humans correctly, because a lot of complications are to be considered or a great calculation depth is needed to see the point. In short, they are impractical, and it's hard to deduct a general strategic pattern/rule from these moves. The goal of "How to reassess your chess" is not to make stockfish-like calculation machines out of you, but to teach you strategic concepts, and his moves are always "good enough" for practical play and learning strategic ideas.
Especially in a book about strategy, there will be alternatives and multiple possible avenues, but he chose one specific line to demonstrate an idea to you. Of course, you may not have to maneuver your knight to that juicy outpost, for example, but it's pretty good to do it and he can prove his point that you sometimes can and should invest the time to get your pieces to good squares.
Yes, there may be another variation the computer might play, but you wouldn't have learned the concept.
In a few years, a new chess engine might laugh at your Stockfish 15, just as Stockfish 15 now laughs at the engines Silman used to write his books.
The strategic principles, however, stay. When you find an example, where Silman is very wrong objectively, you should of course skip this particular example or not take it too gravely (in the example, the move is so impractical for Black that even an International Master would refrain from doing it (even if objectively, the ?? may be wrong, it may be correct practically..).
This is the exception in this book, anyhow.
Should I throw the PDF right now?
Yes, but only for you to read the hard copy. Please buy the book if you can afford it. There are no legitimate (scanned) PDFs from Silman's works. But I would keep reading because you can still learn a lot from Silman.