There is a typo in the MSDN documentation of fopen and its relatives _fwopen, fopen_s, ...
This error exists in both the online and offline MSDN documentation
The open mode for 16 bit unicode is listed as UTF16-LE in the remarks section text. This should be UTF-16LE. Using the wrong value will lead to runtime errors.
The encoding is also mentioned in the table in the remarks section, but there is is listed correctly. The problem is only with the encoding that is mentioned in the text.