Multiple XSLT Steps with Secondary Outputs

I'm unable to understand how the connections should work between multiple xslt steps where each one has secondary output (and so all but the first have a sequence for an input).
XProc Ref has an example pipeline in the p:xslt step documentation that I'll expand for discussion: https://xprocref.org/3.0/p.xslt.html 
My expansion of the pipeline consists in adding a second XSLT step that follows the first and takes as input the sequence of documents output by the first XSLT step (on secondary port). Both XSLT steps should have their sequence outputs written to disk by p:store.  Here's my expansion of the example (minus the XSLT modules that are referenced):
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc" version="3.0">        <p:input port="source"/>    <p:output port="result" />        <p:xslt name="create-secondary-documents-1">        <p:with-input port="stylesheet" href="spec-split-docs-1.xsl"/>    </p:xslt>        <p:for-each name="step1-store">        <p:with-input pipe="secondary@create-secondary-documents-1"/>        <p:store href="{base-uri(/)}"/>        <p:identity>            <p:with-input pipe="result-uri"/>        </p:identity>    </p:for-each>            <p:for-each>        <p:xslt name="create-secondary-documents-2">            <p:with-input port="source" pipe="secondary@create-secondary-documents-1"/>            <p:with-input port="stylesheet" href="spec-split-docs-2.xsl"/>        </p:xslt>    </p:for-each>            <p:for-each name="step2-store">        <p:with-input pipe="secondary@create-secondary-documents-2"/>        <p:store href="{base-uri(/)}"/>        <p:identity>            <p:with-input pipe="result-uri"/>        </p:identity>    </p:for-each>    </p:declare-step>
I've tried every permutation of this I can think of and I can't get any of them to work. I'm sure that I'm missing something fundamental about connections but am not seeing it. Maybe I've got the pipeline concept entirely wrong for the requirement. In any case am asking for folks to enlighten me.
Thanks,
Don