[jdmichal]

> As a side note, we do have some additional points, not shown in the plots, that are used in resolution limited scenarios — such as a streaming session limited to 720p or 1080p highest encoding resolution. Such points lie under (or to the right of) the convex hull main ladder curve but allow quality to ramp up in resolution limited scenarios.

They're showing the curve that is used for connections that want to be streaming 4k. So if you're on the 1080 stream in the charted scenario, it's because you're bandwidth-limited. They have higher-quality, higher-bitrate encoding curves for lower-resolution connections. However, it doesn't make sense to use that 1080 encoding for a 4k connection. If you could afford the bitrate, you'd rather be streaming the higher resolution from the displayed curve.