When a HTML has a wrong encoding set (content="text/html; charset=utf-16") we use the UTF-16 encoding when importing this HTML. This leads to wrong import. 
Microsoft Word detects that the set encoding is wrong and uses UTF-8 instead so that the imported result is correct. 

The HTML5 specification forbids the use of the meta element to declare UTF-16, because the values must be ASCII-compatible: https://www.w3.org/International/questions/qa-html-encoding-declarations#utf16