ID3v2.3 UTF-16 not working for FLAC

When I selected ID3v2.3 UTF-16 and saved the file (*.FLAC), tags still in UTF-8 format...
Need option to force to save the tags in UTF-16 with BOM (as a first character)
UTF16_LE - (U+FEFF)
UTF16_BE - (U+FFFE))

Mp3tag only supports FLAC tags (Vorbis Comments) for FLAC files. The ID3v2 UTF-16 option is for file types that use ID3v2 (e.g., MP3).