From the examples, it looks like WiFiperf is a cnMaestro pro (now know as cnMaestro X) feature. That being said, I have cnMaestro X cloud, and I cannot find the WiFiperf features that the document discusses.
Another thing that the article specifically mentions is that is used for cnMaestro on-premise… no mention of cnMaestro cloud is made.
Are you using cnMaestro on-premise or cloud, and if so, is cnMaestro X trial enabled?