maybe the experts working on this movie know something we don't? Hahah, though that is unlikely...
this is Three Kingdoms, historical accuracy has not mattered very much to Chinese when telling this story. Guan Yu did not in real life wield 100lb blades, or wear Ming dynasty armor 1000 years before those designs came about.
I think sometimes we get hung up on trying to make clear Chinese/Japanese differences. Europeans don't seem to have as much of a problem with telling english or french or italian armor/weapons apart. I'd rather focus on the similarities.
At one point I thought Japanese Noh Masks, the faces on samurai masks were a distinct Japanese thing. But then I got a book on Chinese masks, a section on Tang dynasty Nuo theater and masks... and they looked just like Japanese Noh masks, looked like the fierce demon faces of samurai armor.
I haven't found any info on the internet on Nuo theater. This tells me that there is, there is a lot of research already done, information already compiled, BUT accessing it is still an issue.
Hmmm, if anything, it could be used as a sneaky way for Chinese to slowly claim Japanese related things...
like, see Warriors of Heaven and Earth? The Japanese guy who was a Tang agent, he uses a pair of samurai swords basically. He fights like how samurai fight in Samurai movies.
But towards the end, he talks about his past. He came to Tang as a young boy, has not been home for decades. He talks about how they taught him swordsmanship in the Tang. His samurai swords, his samurai fighting style, in the movie, came from the Tang Dynasty.
and here's a page from a book of Samurai armor written by a Japanese guy

"Chinese inspired"
QUOTE
Late Sengoku to Edo period
Even by this time, not all armor was made to all the latest adopted styles. However, in the Nara period, the then government adopted what was a Chinese-style of armor supposedly similar to the newest designs of the time.
and really it's just a movie, it's Chinese, people will associate it with that. The no.1 reason I've seen little American kids go to the Chinese galleries at the Smithsonian is 'cause they like Dynasty Warriors or kungfu movies.
QUOTE
I'd like to see that. Do you have a link or detailed description?

I used to think armor in rows like that (instead of a single 'sheet'') was a Japanese difference from Chinese armor.