3.3.3.1 getChildren orderBy Input needs significant clarification

The orderBy parameter is not described except to say "see ORDER BY clause in query". The ORDER BY clause is defined in two places (it is not clear which is being referenced) - one is the BNF which simply defines its grammar, the other is section 2.10.2.5, which says:

All column names referenced in this clause MUST be valid "queryName" or their aliased values for properties defined as orderable in the Object-type(s) whose Virtual Tables are listed in the FROM clause.
Only columns in the SELECT clause MAY be in the ORDER BY clause.

None of that applies to getChildren, because:
o There is no FROM clause
o Even ignoring that, there is no single Object-Type being returned here, as the children of a folder are of heterogeneous types (there is not even a cmis root type to capture them all)
o There is no SELECT clause
o Even ignoring that, there is no place where a list of usable property names can be obtained for ordering the results of the service
o There are no aliases

How does orderBy work?
o What properties are allowed?
o How are objects whose types don't define an orderBy property ordered (first? last? excluded?)