[unilynx]

That has always been the case ... requests get logged, and if the server exposes its access logs over HTTP, that's one thing for which a request won't be idempotent

Idempotent etc in the HTTP specs has always been more or less an attempt at a promise to the client "you should be able to repeat this request if you're not sure about success/failure without anyone claiming to implement HTTP being able to throw the book at you".

Just like GETs shouldn't have side effects. But in practice of course, things like https://thedailywtf.com/articles/the_spider_of_doom happen