[xsl] In XSLT 3.0, should the "document" function be available in xsl:evaluate?

["Martin Honnen martin.honnen@xxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

Both the latest internal draft of the XSLT 3.0 spec in 
https://www.w3.org/XML/Group/qtspecs/specifications/xslt-30/html/#dynamic-xpath 
as well as the official https://www.w3.org/TR/xslt-30/#element-evaluate 
say about the function signatures in the context of dynamic XPath 
evaluation using xsl:evaluate: "Note that this set deliberately excludes 
XSLT-defined functions in the standard function namespace".

Based on that I would expect the XSLT "document" function not to be 
available in dynamic XPath evaluation using xsl:evaluate. So I wrote a 
test case doing

<xsl:stylesheet version="3.0" 
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
	xmlns:xs="http://www.w3.org/2001/XMLSchema"; 
xmlns:fn="http://www.w3.org/2005/xpath-functions";
	xmlns:math="http://www.w3.org/2005/xpath-functions/math";
	xmlns:array="http://www.w3.org/2005/xpath-functions/array";
	xmlns:map="http://www.w3.org/2005/xpath-functions/map";
	exclude-result-prefixes="array fn map math xs">
	
	<xsl:output method="xml"/>
	
	<xsl:template name="main" match="/">
		<xsl:sequence
			select="
			let $f := function-lookup(xs:QName('fn:document'), 1)
			return
			if (exists($f)) then
			$f('')
			else
			'not found'"/>
		<xsl:variable name="path" as="xs:string">
			let $f := function-lookup(xs:QName('fn:document'), 1)
			return
			if (exists($f)) then
			$f('')
			else
			'not found'</xsl:variable>
		<xsl:evaluate xpath="$path"/>
	</xsl:template>
	
</xsl:stylesheet>

and expected that to return the stylesheet code for the xsl:sequence and 
'not found' for the xsl:evaluate.

However, only Exselt gives me that result, both Saxon 9.7 EE as well as 
Altova XMLSpy return the stylesheet code twice which seems to indicate 
they make the 'document' function available to xsl:evaluate. Isn't that 
a bug? Or does the spec need to allow it if an implementer wants to go 
beyond pure XPath support?