[kazagistar]

That is not the definition of OOP the author is using. He made it clear what he meant by OOP; a paradigm seen often in production systems. Productive discussions start by accepting given definitions and arguing against the resulting points, not by arguing that the definitions are wrong because they don't match the exact form defined by someone somewhere.

[mpweiher]

No, the premises always need to be examined, not accepted at face value.

If the author is using a wrong definition as a starting point, the rest of the argument is largely pointless...or must be explicitly marked as a hypothetical/counterfactual.

"I define the earth as being an infinite flat plane, from this it follows [for the real world] that..."

Well, no, the earth is not an infinite plane, even if it kinda looks that way, was long believed to be that (maybe minus the infinite) and apparently there still are people who believe that.

[kazagistar]

There is a difference between definition and assumption. An assumption says that something about the world is true. A definition just says what meaning you will intend by a word in the current scope.

When you define OOP, you aren't saying anything about the real world, just stuff about the words you will be using within the current context.