> Yes, the client wanted the server to deliver content it had intended for a different client, regardless of what the service operator wanted, so it lied using its user agent.

I would actually argue, it's not nearly the same type of misconfiguration. The reason scripts, which have never been a browser, who omit their real identity, are doing it, is to evade bot detection. The reason browsers pack their UA with so much legacy data, is because of misconfigured servers. The server owner wants to send data to users and their browsers, but through incompetence, they've made a mistake. Browsers adapted by including extra strings in the UA to account for the expectations of incorrectly configured servers. Extra strings being the critical part, Google bot's UA is an example of this being done correctly.