Compared this vs another comment and its interesting. Pulled the strings directly from the ISO website. I wonder if the 'i' in the lower case one is supposed to be special and not ASCII?

  Python 3.8.10 (default, Mar 15 2022, 12:22:08) 
  [GCC 9.4.0] on linux
  Type "help", "copyright", "credits" or "license" for more information.
  >>> short_name_lower = "Türkiye"
  >>> short_name = "TÜRKİYE"
  >>> short_name.encode()  ## The Ü and İ are UTF-8 chars
  b'T\xc3\x9cRK\xc4\xb0YE'
  >>> short_name_lower.encode()  ## Note only the ü is special, i is just ASCII
  b'T\xc3\xbcrkiye'
  >>> short_name.lower()
  'türki̇ye'
  >>> short_name_lower.lower()
  'türkiye'
  >>> short_name.lower() == short_name_lower.lower() ## Looks the same, but it isn't
  False
  >>> short_name.lower().encode()  ## The i has extra \xcc\x87 here 
  b't\xc3\xbcrki\xcc\x87ye'
  >>> short_name_lower.lower().encode()  ## The i doesn't have the extra here
  b't\xc3\xbcrkiye'
  >>> short_name_lower.upper().encode()  ## So this is wrong too, since its just an ASCII i to start
  b'T\xc3\x9cRKIYE'

Edit: Formatting