"Never ever try to teach about objects as representations of real-world things"

I hear this from time to time—it seems bizarre. Representing real-world things as objects is a fine design approach for many problems and is well worth teaching. Where on earth did the idea that it isn't get started?

SICP, a classic of programming pedagogy if ever there was one, has this to say:

One powerful design strategy, which is particularly appropriate to the construction of programs for modeling physical systems, is to base the structure of our programs on the structure of the system being modeled. For each object in the system, we construct a corresponding computational object. For each system action, we define a symbolic operation in our computational model. (p. 217, 2nd ed.)

It's true that by "object" they mean something more general than OO. But that doesn't change the basic design approach.

It's also true that they are careful to teach more primitive concepts first, so what they do is compatible with the OP's point. But there's a reason why the above passage on real-world representations appears immediately after they mention modularity.