> That shouldn’t be noticeable if the 4K stream was encoded properly. I don't think this is true. At some point there are diminishing returns. At some point if

> That shouldn’t be noticeable if the 4K stream was encoded properly. I don't think this is true. At some point there are diminishing returns. At some point if the 4k video has twice the bitrate it is going to have more information available. Some will be lost in the down sampling but it isn't "improper" to end up with more data on the screen. It is true that YouTube bitrates are pretty "conservative" for the resolution but I don't think that is "improper" it is just a tradeoff based on common device an internet speeds. They could be more bandwidth efficient if they did a custom transcode for each user's screen size and bandwidth but that is infeasible. So it is fine that some users will not be able to stream the 4k transcode on their 4k screen and will need to use the 2k stream and some users will have extra bandwidth on their 1080p screen so will stream the 2k version for better quality. The goal isn't to be perfect for each device but to be good on average.