What! This is essential knowledge. Without it, how can you possibly build a coherent mental model of a program?! I’ve never heard this justification before, it’s bonkers.
EDIT - You have a tree of dependencies. This is something you care about. In order to create that tree in code, you have to convert it to a linear series of statements. This conversion is something you don't really care about as long as you end up with the tree you want. Dependency injection frameworks should make it so you can declaratively specify that tree without having to worry about how it is actually constructed.
The point being made is that just writing the construction statements in the main method is exactly "declaratively specify[ing] that tree", and that "having to worry about how it is actually constructed" is incredibly valuable knowledge to maintainers, because it allows them to see explicitly how components are constructed, and how they interact with each other. It's not something you want to hide with a framework, it's something you want to lift up, front-and-center, so everyone can see it.