[CiNcH]

That's what I expected. All Sony Android TVs use the same SoC. There are actually only 2 HW platforms:

BRAVIA 2015 (ATV1): MediaTek MT5890 (all 2015 models, early 2016 models)
BRAVIA ATV2: MediaTek MT5891 (all models after mid-2016, including 2017 models)

My 4K HDR set is also based on ATV1 with MT5890. So if the VP9 HW decoder is missing for you, this is just a software/driver limitation.