Secondary ports on pipeline need be explicitly declared non-primary?

I made a p:pipeline that had a secondary input port,
called it with "calabash -i source=doc.xml -i what=elem.xml test.xpl", and
it gives me:

> Error  : Pipeline failed: err:XS0030: null  It is a static error to specify
> that more than one input port is the primary.
>
I try a few options, then try Example #2 in http://www.w3.org/TR/xproc/
Same thing, same error message.
Turns out if I put <p:input port="schemas" sequence="true"
primary="false"/>, it works.
This is not the behaviour I expected after reading section 2.3, and the
description of implicit "source" input ports in p:pipelines...
-Leif Warner