> however i'm not sure upto what extent is it standardized in clients to understand that "/path?query" is somehow related to "/path", because originally the request string (path and url parameters) was opaque to the http client, so they should be cached independently. things obviously changed since then.

It hasn't changed. Those two URLs are still cached completely independently by the user agent. The ?time=... cache busting trick is meant to produce a cache key that's never been used before, thus requiring a fresh request. The new request doesn't clean up the cache entries for the old URLs; it just doesn't use them. That's one reason it's better to use etag and such to make the caches work properly, rather than fight them with this trick.

On many servers, if new.html is a static file, the same entity is produced regardless of parameters. But the user agent doesn't know this.