I don't think these hypotheses are in tension. The notion that some scholars, like Plato, distrusted writing based on epistemological theories--the nature of truth and knowing--is well attested. The paper your describing is a sociological description that seeks to better explain the evolution of the institutionalization of writing. Why people behave a certain way, and why they think they behave that way (i.e. their rationalizations), are only loosely related, and often at complete odds; likewise with regards to what people think they're doing and what they're actually doing, or what they're doing at the micro level and what happens at the macro.