Mainly because he has intuitions that are wrong. And as a result he is asking to do things like 'hire 10 offshore developers for less than an intern' or 'because the job market is so bad we should be able to hire google engineers for intern level pay'.
Basically lots of free lunch thinking because he doesn't have as much context on the trade offs. Our project is a pretty basic java application. FAANG engineers are totally overqualified to work on it. The scope is relatively constrained so 10 engineers would be too many cooks in the kitchen.
He doesn't need to know git or rails or anything like that. I got him the Mythical Man month as some people recommended.
Test-Driven Development by Example, by Kent Beck. No other. Kent Beck doesn't even show up on the first page of Google anymore. The book is on page 6. But it's a human way to develop software, dealing with the human limits of the average programmer. The book is easier to read than most of the articles written about it.
The Mythical Man Month by Frederick Brooks. The examples are old, but the wisdom remains. Particularly the chapter (and CACM article) No Silver Bullet-- Essence and Accident in Software Engineering (1986).
Is he making unrealistic requests?
Does he think you are wasting your whole day in notepad instead of doing real work?
When you tell him about a new cool rebase trick in git, he only stares without understanding a word?
Anyway, a book is too long. My recommendation is to try to find some nice post in the old blog of Joel Spolsky https://www.joelonsoftware.com/