The MPEG-DASH IP transmission method unfortunately, by its nature, puts a high load onto the hardware of the receiving device because it breaks the stream up into thousands of file chunks whick then need to be put back together again. It was designed for PC playback in mind, and as we know the processor in TVs doesn't have anywhere near the grunt of a PC. So great for the BBC, and PC users, but when it comes to TVs (which are designed for an international market) when one specific broadcaster decides to go it alone with a new standard it's going to cause support issues.
The same thing happened with Internet radios - Only a few high end models have been released that support MPEG-DASH, but the majority are built for SHOUtcast/ICEcast linear streams only just because that's what the whole world apart from the BBC uses. And so the BBC has had to keep legacy linear radio streams going just because MPEG-DASH is not taking off as fast as they hoped.
I have no doubt that the BBCs approach is technically very efficient, and could eventually take off (particularly if this World Cup trial is a success) but until it proves itself in the open market it will remain peculiarly British with limited support from manufacturers.
As for Sony, as they claimed to have released firmware that supported BBC iPlayer 4K I would hope that they follow through for 2017 devices to ensure that they get to a position where they can guarantee that it works reliably.
