I'm not sure you are really disagreeing. Which is to say I don't see where the not "isn't true" part come from.

Yes classes are closer to the physical reality of modern computer (and that is one reason I prefer C++), but they are still the same construct as a closure and vice-versa. Everything is just implementation details.

Again I grant that languages designed around classes (or really in my opinion, around the physical reality of the device implementing them) are more useful in practice. But from a conceptional abstraction point the post is true.