XSLT 2.0 - 3 Simplified Stylesheet Module

In 3 it is stated, "A simplified stylesheet module is an XML document, or 
part of an XML document ...".

If the outermost element is an html element from HTML 4.01 can the document 
be properly called an "XML document" as in the quote?

Similar questions also arise in connection with the paragraph which follows 
the bullet point from which the quote is taken.

Or, less likely, is the intent that a stylesheet author can no longer use 
simplified stylesheets to create non-XML output?

Andrew Watt