Yes, apparently it's a known unresolved issue with mkgmap tool. Looks like there is actually the option but not autodetected/not applicable if the entire planet is converted at once?
The nonsensical reading I posted in the parent comment was what I actually saw in a free map app that uses OSM data. That conversion tool is apparently used for few apps, and it apparently generate English pronunciations whenever "en" resources are missing and bake it into offline map tile files, but uses some Chinese transcription engine for all Kanji/Hanzi names.
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So, I assume this can be solved two ways: someone can define polygons for national borders, at least for all countries that could experience this problem, such as Japan, China, Korea, Vietnam, etc., and use appropriate transcription engines to generate English readings, either at the OSM side or at the conversion tool side. But that's going to define borders for nations, and therefore I assume that there will be some challenges along that borders since everyone have some territorial disputes.
I don't think this has nothing to do with OpenStreetMap; OSM could have tentative autogenerated name or something for location names that could use English transliteration, as one way this problem can be solved, aside whether it's OSM community responsibility to do so; it's extremely high quality community maintained free/libre map, which is already tremendous. Or it could be done at export tool side, following perhaps more natural division of responsibilities. But regardless, as a non-critical longstanding issue, and a matter of fact, there are actually such exported map files out there with Chinese pronunciations baked in.