https://bugs.winehq.org/show_bug.cgi?id=53582
--- Comment #3 from Nikolay Sivov bunglehead@gmail.com --- It's probably nls data that differs. You can check with WINEDEBUG=+nls log, if GetLocaleInfo* functions are called for abbreviated names. According to [1], "format" variants do use trailing dot, but "stand-alone" variants don't.
[1] https://github.com/unicode-org/cldr/blob/main/common/main/de.xml