Sorting Greek characters

[beerallica]

There's an abnormal behaviour in alphabetically sorted lists containing terms in Greek. The expected order would be Latin characters on top, then Greek; two consecutive lists. However, the Greek list is actually further split into two other lists, one with terms starting with an upper case character and the other with terms starting with lower case. So it's Latin Aa-Zz, then Greek Α-Ω, then Greek α-ω. A real-world example is a tag cloud. See this for example: ​http://www.tastefull.gr/tagcloud

[beerallica]

Update: The lists are five, not three:

1. Latin case-insensitive
2. Uppercase accented Greek
3. Uppercase non-accented Greek
4. Lowercase accented Greek
5. Lowercase non-accented Greek

The database collation is utf8mb4_unicode_ci and phpmyadmin sorts terms OK (e.g. Latin case-insensitive, then Greek case/accent-insensitive).