The short answer is no. The semantic "distance" between two homophones is determined at the discretion of the authors of each dictionary, and it is impossible to draw an official line. Some dictionaries may define 鳴く and 泣く in one entry, while others may define them in two separate entries.
Etymology is an important criterion, of course, but how much emphasis is placed on it depends on the policy of the dictionary. A dictionary that focuses too much on etymology may not necessarily be handy for everyday use by modern speakers.
Nevertheless, I agree most dictionaries explain 青い and 蒼い in the same entry, but 熱い and 厚い in separate entries.
EDIT:
Word |
Meikyō |
Daijisen |
Kōjien |
あつい |
3 [暑][熱][厚] |
3 [暑][熱][厚] |
2 [暑/熱][厚] |
はやい |
1 [早/速/疾/捷] |
1 [早/速/疾/捷] |
1 [早/速/疾/捷] |
つとめる |
3 [務][努][勤] |
3 [務][努][勤] |
1 [務][努][勤] |
なく |
2 [泣][鳴] |
1 [泣/鳴] |
1 [泣/鳴] |
あおい |
1 [青/蒼] |
1 [青/蒼] |
1 [青/蒼] |
As for あつい, Meikyō and Daijisen define 熱い, 暑い and 厚い in three different entries, which is perfectly understandable to me. Kōjien defines 熱い and 暑い under the same entry, which is perfectly understandable, too. As for はやい, all the three dictionaries I checked define 早い, 速い (and 疾い, 捷い) in one big entry, but Meikyō explains when to use which kanji in detail.
Basically, you won't know until you actually look it up in each dictionary. We can only guess, but Meikyō is a relatively small dictionary designed to provide practical explanations for learners of modern Japanese, so they may have thought 暑い and 熱い are different enough practically. Kōjien is an authoritative large dictionary with lots of trivial or obsolete definitions, and they may have thought 暑い and 熱い are the same word etymologically. Daijisen is somewhere between the other two. Ultimately, it's up to the policy of each dictionary.