I have a shield pro 2019. Fantastic device, especially for the lossless audio, and all its ports.
I also have a chromecast with google tv, a 50 USD device. How can this small dongle force dolby vision on every thing and even make SDR look that good? I'm confused.
I would consider forcing Dolby vision on everything a bug, not a feature :D. But the answer is these devices use specialized hardware for video decoding and processing that's very efficient. The shield is a more powerful general computing machine that can be updated via software to do things it couldn't at launch, but the CCwGTV is very good at what its hardware supports out of the box. The chips these dongles use get better every year, with more supported features and faster clock.
I knew about the shield not supporting HDR10+ & YouTube HDR (because of not supporting vp9 profile 2), but this is new.
Most probable reason is that the hardware of shield hasn't changed much since 2015