Just as a follow up, I've been in frequent contact with Ezcoo about the lack of Dolby Digital on the Ezcoo splitter, they even had their engineer send me pictures from the lab showing it working on their 55" OLED. They ended up sending me a new one straight from China and sure enough, I just tested it and it does indeed pass Dolby Vision without any problems now (possibly new firmware I guess?). Very impressed with their level of customer support in trying to get this to work.
Only challenge I still have is that it doesn't strip HDR from the scaled output, so the signal sent to Hyperion on my PI is pink/white and distorted. So while it works fine now w/ my LG OLED when connected, since the scaled output retains HDR its not usable for Hyperion. Not sure if there is a way around that yet, is there?
Also, on a side note - anyone else see that HD Fury has added HDR to SDR conversion into the HDFury4? Interestingly enough, they are also testing adding LED capabilities directly into the box by integrating an LED driver and using the 3d output. Its $279, but it could end up being a one stop solution - https://www.hdfury.com/product/hdfury-x4/