If the value of the man.charmap.enabled parameter is non-zero (the default), keeping the man.output.encoding parameter at its default value (UTF-8) or setting it to UTF-16 does not cause your man pages to be output in raw UTF-8 or UTF-16 -- because any Unicode characters for which matches are found in the enabled character map will be replaced with roff escape sequences before the final man-page files are generated.

So if you want to generate "real" UTF-8 man pages, without any character substitution being performed on your content, you need to set man.charmap.enabled to zero (which will completely disable character-map processing).

You may also need to set man.charmap.enabled to zero if you want to output man pages in an encoding other than UTF-8 or UTF-16. Character-map processing is based on Unicode character values and may not work with other output encodings.