devtrackers.gg
Okay, hear me out: what if it's just a game with some random lore that a writer came up with without any intention of connecting it to our world? Isn't this the most likely explanation? What would be the point of connecting the story to our reality? I'd expect to actually avoiding any connections so that players don't feel any personal connection to either faction in order to randomly balance them out.
You're just seeing patterns, because our brains are wired to do so. Secondly, none of your points is particularly strong; e.g. Caoivish would be an adjective in English based on Caoiva, and English has deep roots in Latin anyway. Basing propaganda on something like honour is expected, even native American tribes did that, AFAIK. Etc.
I can assure you that nothing in Foxhole is random.
All world-building is a mix of influences. Humans are horribly bad at inventing entirely new, unseen concepts. Most western fantasy (a la Tolkien) takes myths and legends and medieval history, puts it in a blender and makes a nice little smoothie out of it.
Foxhole is not inspired by the conflicts of WWI and WWII aside from, obviously, equipment and era (much like you'd see in fantasy with swords and shields and tactics). It is an original setting. Patterns are intentional. There isn't a single thing in the lore that has been put there without consideration for how it relates to the history of the world.
My thought as to why this is hard for people to parse is that it is recent enough in history that we have photographs and video depicting the era, whereas pretty much anything prior, we don't.
But to your point, all fiction is inherently something 'a writer came up with.'