The per_page query param seems to have no effect

According the JSON response of /top.json?period=weekly, the “next” page would be under /top.json?page=2&per_page=50&period=weekly

That gave me hope that I could alter the per_page value to 1 or any lower (or even higher) number, but, it does not seem to take any effect.
For example /top.json?period=weekly&per_page=1 still returns 50 “top” topics.

My goal is to retrieve just one (the newest) top topic.

Is the per_page argument only “decorative”?