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 you linked 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.