Last time I checked it worked perfectly for me on OrangePi Plus 2E. Anyway, your issue seems like issue in DRM driver and not in VPU driver. VPU in both cases (downscaled or not) outputs same image, but DRM driver is responsible for downscaling and outputting it on HDMI. Can you make a photo of issue?
I found my issue. I try to play 10bit 4k H.265 on my OrangePi Plus 2E which is not supported.
My filenames were just wrong and I did not check them with another program.
Thank you very much for your response.