Reports an error if the compiler is called with the phase parameter set to #DEFAULT.

[dmj]

5.4.10 phase element
..
Two names, #ALL and #DEFAULT, have special meanings. The name #ALL is reserved to denote that all
patterns are active. The name #DEFAULT is to denote that the name given in the defaultPhase attribute
on the schema element should be used. If no defaultPhase is specified, then all patterns are active.

NOTE The names #ALL and #DEFAULT shall not be used in a Schematron schema. They are for use when invoking or configuring schema validation, for example, as a command-line parameter.

From my interpretation this means the the Schematron should defaultPhase or all patterns when called with the parameter phase set to #DEFAULT.

This is covered by https://github.com/dmj/schematron-test/blob/t/more-tests/phase/phase-02.xspec