I think in the end the author's only complaint was that it was difficult to figure out what bitrate the Chromecast was streaming at, is a pretty minor problem. It reads like a complaint post, but that seems to just be the author's writing style.

You're technially right but conceptually he did show that the bitrate isn't in the normal 4k ballpark.

There's likely little or no benefit on using a 4k resolution at this bitrate.

In his experiment the Chroomecast on wifi gets a ~6 Mbps stream for 4k, which is about 20% of an average quality Handbrake encoded 4k stream. The surprise was that in his experiment Apple TV got so much higher bitrate. Market segmentation?