i can relate to this.
playing 4k hdr video, mpc-hc and madvr, windows 10.
im checking the stat, madvr reported no dropped frame (playing at 2xvideo fps and 72fps fixed).
svp setting loaded succesfully upon playing video but both video fps mode doesnt feel smooth and just like playing at the original 23fps.
edit:
i noticed after carefully wathing the video, that smoothness only appears sporadically
looks like having something to do with motion vectors grid?
i tried with 4px at first and theres barely any smoothness.
smoothness constantly appeared at 16px upwards