Recently I've been using the スーパー大辞林 Japanese dictionary, because it is built-in to all my Apple devices. But I frequently find words where there is a single entry in the dictionary, but 2 or 3 different kanji "spellings" are listed.
For example, if I search for 空く, I get this page which claims to be the entry for 開く, 空く, and 明く all at the same time. Does that mean that all 3 of those words have identical meanings? It looks like some of the definitions are reserved for only one of the kanji. Like in my search, definitions 1 and 3 are marked 《開く》 and definition 4 is marked 《空》. Does that mean that to use 空 to convey the meaning from definition 1 is incorrect? If that's the case, why don't they have separate dictionary entries?
Are these entries indeed homonyms, in that they have the same pronunciation, but unique, independent meanings, and it is these unique meanings that gave rise to the separate kanji to begin with? That would seem to argue for their dictionary entries to be separate.