Long story short: open the files in a hex editor and change dvh1 to hvc1 and they will play in HDR just fine. Apparently the MOV files played fine on Kodi before, but somewhere along the way Apple changed the FourCC (codec ID) from hvc1 to dvh1 (which is a brand-new Dolby Vision-specific one) that the current version of ffmpeg (which Kodi uses as its player doesn't recognize). Update: Ok, I feel like an idiot after wasting hours on this.
Anyone know how to convert the HDR versions to MP4 so they'll play in Kodi? I have an HDR-compatible device and I swear I did this with ffmpeg in the past, but simply doing something like ffmpeg -i comp_DB_D001_C001_PSNK_v06_HDR_PS_20180824_HDR_4K_HEVC.mov -vcodec copy comp_DB_D001_C001_PSNK_v06_HDR_PS_20180824_HDR_4K_HEVC.mp4 doesn't work because it doesn't include the necessary metadata to flag the video stream as being HDR.