There is no problem with the rewrite rules.
Two possibilities, one is that browser cache the page, you can verify it with LiveHeader extension, if browser uses a cached page, there should not be any new request sent. You can verify that at server end with access log as well.
Another possibilities, is browser cache the cookie value, you should be able to verify it with LiveHeader.
You can also turn on rewrite log at server side to verify the rewrite rules.