When rename file in Finder and use symbol й
U+0439 : CYRILLIC SMALL LETTER SHORT I
it is then converted to a combination of two unicode characters by macOS/Finder
U+0438 : CYRILLIC SMALL LETTER I
U+0306 : COMBINING BREVE {short; Greek vrachy}
Does anybody know why it is so? Such behaviour causes troubles to regular expressions on different web pages as they can't detect й as a correct cyrillic symbol.
My macOS version is 14.1.2 (23B92).