…it came in HLS which can't be streamed to an AppleTV.
HLS (.movpkg) is unfortunately not supported for Home Sharing at this time. AirPlay would still work, though. You can give feedback to Apple that users want this for their iTunes Store downloads. It does not appear to be an Apple TV issue per se: Home Sharing to iPhone or iPad also doesn’t list these HLS downloads: I believe it is already excluded for Home Sharing on the Mac.
Previously (in macOS Catalina 10.15) users could de-select HDR, and select Most Compatible, and simplify the audio options, to force M4V file downloads. That former option (HDR) is no longer available in Big Sur or Monterey. You can give feedback to Apple that Home Sharing users want M4V download options.
Also see:
discussions.apple.com/thread/254270416
discussions.apple.com/thread/254277354
Apple support was very nice but can't fix it since the file came from the studio.
Well, that is not really true, as it would download in .m4v format on (older) devices/OSes that can’t handle HLS. That .m4v wouldn’t be in HDR, or include other fancier options, though.