If you read back on this thread, SOMEWHERE they dexcribed this in detail. I will paraphrase.
Intel gets the information, and puts it in the cache (which one I don't know) Then when its ready to execute, at that time its checks privs. If its not allowed it does not continue, but by then, if you read the cache, that cats out of the bag. And this all happens in nano-seconds. So if you read the cache, and write the results somewhere that you can read in the future, you are in, and the information is leaked. AMD checks before it loads the cache.
Again, that a laymans paraphase of what I read.