Can't confirm or deny others, but Subnautica is definitely ~3.5. There is, however, a buggy EU/UK version that can sometimes incorrectly download multiple language files that push it to 5 GB. But the non-buggy US version is around 3.5 GB.I’m not sure about how accurate some of these numbers are as the guy pulled them from the store page although PS5 definitely tends to have an advantage overall.
Hitman 3 is 64.9GB with everything installed on XSX not 77.8GB.
Subnautica is 5GB on PS5 not 3.8GB.
Immortals is 30.49GB on PS5 not 22.3GB.
Tony Hawk is 22GB on XSX not 31.9GB.
Valhalla on XSX is right but the PS5 version is apparently 61.5GB not 41.8GB but I cant check that.