Saxon

I get some strange (diagnostic?) messages like

Balance l=2 r=1
Balance l=2 r=1

when using Saxon 9.9.1.6 HE Java from the command line and run code like the one attached and shown at the end.

I am not sure what they are supposed to tell me or how to switch them off, they appear even when not running with the -t option.

declare namespace map = "http://www.w3.org/2005/xpath-functions/map";
declare namespace array = "http://www.w3.org/2005/xpath-functions/array";

declare namespace output = "http://www.w3.org/2010/xslt-xquery-serialization";

declare option output:method 'adaptive';

declare function local:fold-left-append($seq as item()*, $zero as array(*)) as array(*) {
  if (empty($seq))
  then $zero
  else local:fold-left-append(tail($seq), array:append($zero, head($seq)?*))
};

declare variable $xslt1 :=             

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    xmlns:array="http://www.w3.org/2005/xpath-functions/array"
    xmlns:mf="http://example.com/mf"
    exclude-result-prefixes="#all"
    version="3.0">
    
    <xsl:mode on-no-match="shallow-skip"/>
    
    <xsl:output method="adaptive"/>
    
    <xsl:function name="mf:fold-left-append" as="array(*)">
        <xsl:param name="seq" as="item()*"/>
        <xsl:param name="zero" as="array(*)"/>
        <xsl:sequence
            select="if (empty($seq))
                    then $zero
                    else mf:fold-left-append(tail($seq), array:append($zero, head($seq)?*))"/>
    </xsl:function>
    
    <xsl:template match="root/items">
        <xsl:variable name="sequence-of-arrays" as="array(node()*)*">
            <xsl:for-each-group select="item" composite="yes" group-by="foo, bar">
                <xsl:sequence select="array {{ current-group() }}"/>
            </xsl:for-each-group>            
        </xsl:variable>
        <xsl:sequence select="mf:fold-left-append($sequence-of-arrays, [])"/>
    </xsl:template>
    
</xsl:stylesheet>;

let $xquery-result := 
    local:fold-left-append(
        for $item at $pos in root/items/item
        group by $key1 := $item/foo, $key2 := $item/bar
        order by head($pos)
        return 
          array { $item },
        []
    ),
    $xslt-result := 
    transform(map {
        'source-node' : .,
        'stylesheet-node' : $xslt1,
        'delivery-format' : 'raw'
    })?output
return
    deep-equal($xquery-result, $xslt-result)