Section 4.3.3 and Appendix F of the XML 1.0 spec speak about UTF-16, the byte order mark (BOM) in UTF-16 encoded data streams, and the XML encoding declaration. From the information in those sections, it would seem that a byte order mark is required in UTF-16 documents. But the summary chart in Appendix F gives a scenario where a UTF-16 input does not have a Byte order mark, but this scenario has an xml declaration. According to section 4.3.3, a UTF-16 encoded document does not require an encoding declaration (and the XML declaration itself is optional in such a case).
Given this information, is a UTF-16 xml document with neither a BOM nor an XML declaration that also lacks externally provided encoding information considered well-formed if the rest of the document is?