HLG and HDR10 are static, Dolby Vision and HDR10+ are dynamic (picture settings can be changed for each frame, although mostly changing them per scene is enough).
https://www.cnet.com/news/hdr10-vs-dolby-vision-vs-hlg-how-do-hdr-formats-compare/
Gave CNET a very thorough read. It seems Dolby Vision is a good bonus to have, one that can make a difference, but not dealbreaker. If the AppleTV is updated to process the Dolby Vision and send it to the TV, then great. It will certainly eliminate headaches for people shopping for TVs and checking if their selections include DV or HGL/HDR10.