i fear NDI is not your weapon of choice for these kind things.
as you already assumed, NDI is applying some agressive, proprietary compression on the image to achieve a low bandwith (i.e. several fullHD streams over gigabit ethernet are possible). it is highly optimized for the CPUs vector extensions (SSE etc.) to for low latency video streaming. i’m not sure if you have a lot of choice regarding the transmitted video formats but i’m pretty sure it preferres “visual quality” over “technical correctness” and assumes plain broadcast video images…
anyways, i would have to look into this deeper to be sure (an update to NDI 3.8 is nescessary anyways - when there is time for that i will have a look).