While you are right that one logical font can consist of multiple font files (or possibly a OpenType collection), this constraint does affect most typical fonts, and in particular wide-coverage CJK fonts already hit this limit. Fonts supporting only one of Chinese, Japanese and Korean don't need that many glyphs, and probably even two of them will be okay, but fonts with all three sets of glyphs won't. It is therefore common to provide three versions of fonts, all differently named.