Right, prior to "dictionary-ization" you could have variant spellings etc. You're correct about prescription. It's an interesting idea, how to understand authority in these contexts.
Transitions in media and writing - you could take Charlemagne's attempts to standardize HRE script in the administrative state as a sort of "standardization of Empire," the development of English as the web's lingua franca, the role of the Stationers' co. during the development of early printed media as standardization of surveillance, the history of copyright law, all that - were in many cases state power responding to their inability to control both the infrastructure and content of communication. We're not afraid a chatbot is going to use an unrecognizable typeface in communication with another chatbot, or publish dissident pamphlets and spread them to other chatbots. We're afraid our literate practices will atrophy from outsourcing. That we start to communicate like the chatbot.
Put it this way: if you had everyone learn the five-paragraph essay style, you'd have the same lack of voice; and, boy, did "we" (US) ever get that exact consequence. You raise an interesting point about "standards" in that respect because that's a specific ideological, state-driven attempt to prioritize and measure skills. But if you tell students to write without that specific priority, they lose all sense of writing. So it's destructive, there's an expressive issue there. So, yeah, as you say: "even worse." They forget a skill they never had.
I'm just wondering, I guess, about the harm. The past has these examples of standardization in the West and if we say "well this is just another case of a historically prescriptivist tendency in writing" I guess that's fine, but we don't really look at these examples as beneficial or with a shrug. We don't even want everybody writing like EB White , we certainly don't want everybody writing like Elon Musk.