I remember trying the 2160p versions with VLC and the colours looked really off compared to the 1080p. Instead I tried MPV player on Windows, and it looked much better.
I guess you are on Mac, if you are using IINA. I never really used Mac, so I don’t know what alternatives there are, or if there’s any way to make IINA handle the HDR better.
Is there a media player classic or MPV?

Just did a quick search and looks like there is “Unofficial third-party builds” of MPV. Maybe try that?