The paper does not specify message passing or reflection, both of which are essential to OOP. I think OOP lost its way as soon as C++ reinterpreted it in terms of only encapsulation, inheritance, and polymorphism.

According to Alan Kay (one of the creators of Smalltalk, the first OOP), message passing is more important to OOP than inheritance. If you listen to his old speeches, what he is describing sounds a lot more like microservices and VMs/containers than what most of the later languages turned it into. (He describes objects as "mini computers" that interact with each other using only public interfaces)