One theory I heard was that Japanese has a rather limited set of syllables, so the ambiguity is greater. In spoken Japanese some of the ambiguity would be reso

One theory I heard was that Japanese has a rather limited set of syllables, so the ambiguity is greater. In spoken Japanese some of the ambiguity would be resolved by pitch accent, but accent is not written in Hiragana/Katakana. On the other hand, Korean has a relatively large number of syllables (so less ambiguity), and modern Korean spelling system is highly morphophonemic (which is a fancy way of saying "words that sound the same in a form may still be written differently, depending on how they sound in other forms"), which also helps a bit. For example, the words 낫 (scythe) 낮 (day) 낯 (face) all sound the same when in isolation (or when followed by a consonant), but sound different when followed by a vowel.