That's fair and I agree that the OSI model is not useful for a precise understanding of deployed networking technology. I do think it is useful as an architect

That's fair and I agree that the OSI model is not useful for a precise understanding of deployed networking technology. I do think it is useful as an architectural device or a conceptual design goal -- i.e. a model to model your models on. :) But I also concede that part of its teaching value is that it is a failure in practice. It was a formalization of the ad hoc (successful!) design strategies of early networking. I see echoes of it everywhere, most obviously in the Linux kernel, and I think it's valuable for that.