I've been here in Japan since 2009, almost half of my entire life, I speak the language fluently and often understand concepts and such better in Japanese than English. All this to say, this really has nothing to do with me holding onto western preconceptions. If you were to actually read what I'm saying to you- even common Japanese are often counting each individual units of large numbers (as I gave as an example; "123,456,789,123,456" in order to figure out how to read them correctly. It's not a matter of difficulty in understanding the number and where it divides in the Japanese numbering system, it's just a matter of correctly reading out the number, figuring out what the biggest unit is, there's a difference between the two.
If you continue to argue "it's easy bruh" at me after all my explanations of what I'm actually saying, I honestly have no more to say to you. You're arguing against something different to what I'm saying.
I've also lived in Japan for years. I've had to talk numbers with colleagues every day in Japanese for programming. I've never experienced what you describe, nor felt like anyone else had this kind of thinking, or more specifically had trouble with it. When I think a number in Japanese or Chinese in my head, I don't struggle with this.
Look, you keep referring to it as a unit, when it's not. I don't know what you've learned, or how you decide to interpret it. You're really just describing how people in other countries have to count individual "units", then realize they should say "thousand", or "million" or whatever is the equivalent. What's the bloody difference, except that you've decided to remember both systems? These "units" are just shorthand for a given magnitude. Isn't the confusion solely on you then?
If you want to say that we're just saying "it's easy", then you're really just doing the same, saying it's hard, in which case yea, maybe we'll never end this argument. I don't really care how you feel about it, take it as I'm pointing out to for the benefit of others something perfectly logical: it's the same effing shorthand concept as western naming, only it's actually in fewer characters and a slightly different magnitude. I can write 10 million (as most people do online, for work or for signage) or ten million in English, or 1,000万 (same reasons as English) or 千万 in Japanese, what's the difference in writing or thinking any of the 4 examples? Almost none. Everyone counts out the numbers to say the "unit", in every relevant language.
If you find it hard....whatever.