I tried the following stylesheet:

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    version="3.0">

    <xsl:mode streamable="yes"/>

    <xsl:template match="/">
        <xsl:apply-templates select="
            unparsed-text-lines('test.xsl')" >
        </xsl:apply-templates>
    </xsl:template>
   
    <xsl:template match="~xs:string">
        <xsl:value-of select="., '&#xA;'" />
    </xsl:template>
</xsl:stylesheet>

The stylesheet runs correctly when using streamable="no", but it throws the following exception when running it with streamable="yes":

Description: Fatal error during transformation: java.lang.ClassCastException: Unable to cast object of type 'net.sf.saxon.type.BuiltInAtomicType' to type 'net.sf.saxon.pattern.NodeTest'.

I used both 9.5.0.2 (Java, licensed) and 9.5.1.1 (.NET, trial) version of Saxon EE, both raise the same exception.

Cheers,
Abel