That's rather curious to say the least. I can tell you that say on Taobao, you can buy WWII plastic model, you know it's a big hobby in Japan and all over. But models of Japanese and Germany fighters and tanks etc would have their Taobao page's photos partly obscured for the Nazi and Imperial Japan insignia. Some seller even went the extra extra mile and applied the same treatment to US and USSR military symbols (yes I have seen the red star being censored). Of course it's legal to buy the product, and the logos and decals etc are accurate, but the Taobao page for selling the product would be mosiac'ed.
Which reminds of a totally silly censorship. I got a plastic model kit of a hentai nature, (it's Japanese btw) the model contains various objects like dildo, naked breasts with pre-painted nipples and decals for pubic hair. The exterior box, obviously, shows these features with censorship. But even the instruction manual for putting the model together has these offensive images mosaic'ed, But I'm holding the 3-D colored versions in my hands, and the 2-D black-white printed instruction is censored. Really silly.
I'm very curious which vid you are working on, even which scenes and which lines. I'm under the impression that JAV rarely talk about "Japan", unless there's an explicit reason to, like when the performer is a haafu, or foreign-born Japanese. For example "Japanese" is not written as Japanese 日本語 in Japan, it's usually written as national language 国語. Similar in China, most of the time 中國 China is not mentioned explicitly, more often to say country 國家 when actual meaning is China.
Anyway... it's very legit question if Chinese subs sanitize the wordings. E.g. chinpo, manko, The former is uniformly translated as "肉棒" meat rod, but it's a euphemism that almost no one uses in real world. Common folks would use 鷄巴,鷄鷄,屌 etc, which is cock or dick. Some (not all) Chinese subbers also seem to avoid the explicit word 精 semen. I suspect (but not sure) it's much more often said out loud some dirty words in JAV. Or I could be mistaken? Yasashi and Ikku are certainly rather "polite" compared to Western dirty talk.
As for historical scar... hmm I've never heard of it affecting JAV consumption. There was that one time that 美竹すず Suzu Mitake (when she was between contracts) went to Taiwan to film uncensored porn. The whole plot was a kind of "revenge" for all the wrongs Japan done to China (specifically for something during the Tokyo Olympics). The whole 3-way geopolitical twisting and contortion is too much for my brain to process, let alone trying to explain on here. Let's just say I find that piece of porn rather difficult to fap to.
ANYWAY WWII-scar and geopolitics isn't the be-all and end-all of China-Japan exchange. Esp. as far as JAV is concerned, it's very fluid, if you catch my meaning...