I don't know why you impart some magical quality on the syntax a->b() such that this causes b() to be a "part of" a. b() being part of a is something conceived in the programmer's mind, not an artifact of the way it's written.
I don't think of it that way, at least. To me, OOP means polymorphism.Quote:
That is how most people differentiate OO from procedural programming. The object has the functionality, versus the function takes objects. I don't know. To be honest, I never got the whole appeal of OOP. It just seems to me like it's an attempt to make sure people don't pass stupid things to functions.