This thread really doesn't have many useful informations.
1) Are you using RO or ROHQ? (or even custom)
1b) If ROHQ, does RO show the same behaviour?
2) Do you have Hardware accelerated video decoding active?
2b) Does it show the same behaviour if you turn it off?
2c) How do older builds behave if you use it with/without HW decoding?
3) If ROHQ, did you fiddle with the madVR settings at all, possibly the deinterlacing settings?
As a general rule, the GPU can only perform certain types of deinterlacing, and the same deinterlacing is usually performed no matter who does it.
I do however know about some problems with rather old NVIDIA systems and combining CUVID decoding with certain renderer functions, but i don't think it only showed as worse deinterlacing, it usually had rather severe problems then.
When i was developing the CUVID decoder for NVIDIA cards, i specifically compared it to EVR's deinterlacing, because thats usually the best the GPU can do.