Itemset pointing to non-relevant nodes

form.xml

<xh:html xmlns:xh="http://www.w3.org/1999/xhtml"
      xmlns:xf="http://www.w3.org/2002/xforms"
      xmlns:xxf="http://orbeon.org/oxf/xml/xforms"
      xmlns:ev="http://www.w3.org/2001/xml-events"
      xmlns:xs="http://www.w3.org/2001/XMLSchema"
      xmlns:fr="http://orbeon.org/oxf/xml/form-runner">
    <xh:head>
        <xf:model>
            <xf:instance>
                <instance>
                    <choice/>
                    <colors>
                        <color>red</color>
                        <color>blue</color>
                    </colors>
                </instance>
            </xf:instance>
            <xf:bind ref="colors/color" relevant="not(exists(@reasonable[. = 'false']))"/>
        </xf:model>
    </xh:head>
    <xh:body>
        <xf:select1 ref="choice" appearance="full">
            <xf:label>Your choice of color</xf:label>
            <xf:itemset ref="../colors/color">
                <xf:label ref="."/>
                <xf:value ref="."/>
            </xf:itemset>
        </xf:select1>
        <xf:trigger>
            <xf:label>Remove unreasonable choice</xf:label>
            <xf:insert ev:event="DOMActivate"
                       context="colors/color[. = 'red']"
                       origin="xf:attribute('reasonable', 'false')"/>
        </xf:trigger>
    </xh:body>
</xh:html>