SYSML2 — validateStateDefinitionIsParallelGeneralization and validateStateUsageIsParallelGeneralization constraints are too restrictive

The validateStateDefinitionIsParallelGeneralization and validateStateUsageIsParallelGeneralization prohibit parallel state definitions and usages from owning specializations of non-parallel state definitions and usages (and vice versa). However, this would prevent even, e.g., an empty non-parallel state definition from having a usage that was parallel, for example:

state def S;
state s : S parallel {  // validation error!
    state s1;
    state s2;
}

Further, it is also a validation error for a parallel state definition to explicitly specialized the base state definition StateAction (which is not parallel), even though an implicit specialization is not checked:

state def S1 parallel { } // legal, implicitly specializes StateAction
state def S2 :> States::StateAction parallel { } // validation error!

For consistency, it would seem that, at least, a parallel state definition or usage should be able to explicitly specialize a non-parallel one. But perhaps the constraints are really not semantically necessary at all.