More likely the translators, probably native English speakers, intentionally decided to use 'authentic', 'historical' Chinese names (as modern mandarn speakers would write them in pinyin) rather than the Japanese ones?
I agree that the effect could be really confusing though, and it's not what I would do!
(IIRC the fan translations of the Manga also gradually decided to change to use Chinese versions of the historical names, which I also found confusing - especially as they have kept some of the old Japanese names ones, so...it's a weird mix...)
Kingdom at least has some connection to historical places/people so it kind of makes sense.
Thunderbolt Fantasy on the other hand is completely original/fictional in setting and characters, and yet still uses the Chinese names in the subtitles. While it is a joint Taiwanese-Japanese project, the only available audio is Japanese. So none of the completely made up names ever match between audio and subtitles.
And then there's Dragon Ball with e.g. Son Goku who is named after the Monkey King from Journey to the West but nobody ever refers to him as Sun Wukong.
For instance the current PRC chairman, Xi Jinping, has an alphabet reading close to Chinese, but Japanese news will call him along the lines of "Shu Kinpei", which sounds absolutely nothing near the original name, but is how someone would read the name assuming it was Japanese and with no pronounciations hints. They just don't care much about the sounds when it comes Asian names, even in official settings.