2.1.64 Part 4 Section, textboxTightWrap (Allow Surrounding Paragraphs to Tight Wrap to Text Box Contents)

a.   The standard describes that the val attribute on the textboxTightWrap element takes one of five values: none, allLines, firstAndLastLine, firstLineOnly, and lastLineOnly.

Word always resets the value of this attribute  to allLines when opening a document.