A commenter, richcon, on the linked story makes a good point: " The open source HEVC software decoder requires a four-core Intel Core i7 running at 2.3 Ghz to play 30p 4k video, and I'd guess it'd be running so hot you could fry an egg on it. The Retina iMac only has an i7 chip in the maxed-out upgrade configuration. So maybe it is about the hardware performance. If Amazon paid for it they could license a commercial…
If I was Netflix I wouldn't want to release 4K if it meant only a small segment of customers would get a good experience. Releasing a disclaimer that the user requires adequate hardware won't satisfy the majority of computer users who don't know or care about the specs required. Most people just want it to work.
I also take issue with the line, "Anyone who knows technology knows the computational and image-processing capabilities of even an average PC or Mac far outstrip those of a streaming box." Dedicated hardware can outperform a general computer while requiring less "processing power" (measured in FLOPS or GHz or whatever). The Chromecast has a dual-core CPU and 512 MB of RAM and it runs HD video perfectly.