Issue found on page 'Utility Functions': ICU_SORT_KEY is not very clear

[manticore-projects]

select icu_sort_key('ö', 'de')=icu_sort_key('o', 'de');
/* returns: FALSE */

select icu_sort_key('o', 'de:ci')=icu_sort_key('O', 'de:ci');
/* returns: FALSE */

I would have expected, that this example returns True since in German O and O-Umlaut have the same order? Also I am not clear how to get case insensitive Collators?