While I agree that Chen was gifted 4th, and should have been behind Hendrickx/Sakamoto, Kaori didn't exactly do herself favours either. She should have done a 3L in the SP instead of her flutz, giving up 2 points there. She also flubbed her final FS spin which if it were a level 4 would have given her 4th place. At any rate it doesn't really matter because if Chen coming in 4th at Worlds doesn't make her a great skater to you, so it's not like Sakamoto coming 4th would have made her a great skater either, right?
Also, this "Japanese are criminally underscored" narrative is getting pretty yawn-worthy. The Japanese women were still rather gifted with PCS at Worlds. Sakamoto still got 68 PCS, which outside of Japan is about as good as she should have been getting last season - sorry she's not a 70 PCS clean skater yet (although I don't think a clean Liu/Trusova/Valieva/Tuktamysheva are either), but I get the Japanese #1 PCS boost. Also, technically speaking, Kaori was gifted with the non-flutz calls - you can especially see it at 0.25x speed at this angle
https://www.youtube.com/watch?v=b9N1FFqQm-s#t=4m53 or even this angle
https://www.youtube.com/watch?v=vrfrWuYsyQY#t=1m18s - very clearly an inside edge on takeoff, and yet she went from an e to a ! (although that was home ice so maybe internationally she'll actually get called on it).
At 2021 Worlds, Kihira somehow got 69 PCS with several errors including a fall on her last jumping pass (half her jumping passes didn't get +GOE). Miyahara is always lovely to watch, and perpetually one of my fave skaters, but even I have to acknowledge that she had two falls, two pops, several </<<, and was still awarded 63 PCS (including 8.5s... really?!). In the SP she had two major errors (fall and singling a combo) and still garnered almost 34 PCS. So I'm not seeing where this "they don't get favourable judging" narrative is coming from if we look at Worlds.
Yes, the Russians and Americans are often overscored (I certainly don't think any of them clean are good enough skaters/programs to be pulling mid-70s, except maybe 2019-2020 season Kostornaia whose programs just aren't doing it for me this year. And I also think Russian skaters are definitely more overscored relative to Japanese skaters (due to their considerable technical superiority) — but it's not like the Japanese aren't ever being thrown carrots either. They're just, as you said, underperforming technically speaking and the system forces poor technical performers to not get huge scores even if the judges try to save them on PCS. I also find that each Japanese skater has something that the other Japanese skaters needs - Sakamoto needs Matsuike's non-stiff arms and Miyahara's finesse, Mihara and Matsuike needs Sakamoto's projection and speed, Miyahara needs Sakamoto's jumping ability, Higuchi needs more consistency and avoiding pops, and Rika needs to be healthy. Nobody's "total packaging" it at the moment, the closest being Sakamoto.
edit: Also not that it needs explaining, but I went over Liu and Matsuike's programs again and I can't imagine how you could even put them on par. Liu skates with much more speed and has far more transitions in/out of her jumps and within her program. Her spins are also faster with better positions and centering. The judges were even pretty correct with her scoring I thought given that she skated "clean" with no visible errors (aside from the URs which she was marked down for, so you can't even argue they held her up there).