Can barbiturates be prescribed for reasons other than the criteria stated? such as butalbarbital for catatonic schizophrenia

No: Barbiturates are not the treatment of choice for schizophrenia. I have sometimes used low dose Ativan (lorazepam) to help severely catatonic people eat, though. With this, they would have just enough movement to be able to take in a meal. Still, this is not the overarching main treatment for their illness either -- it's symptomatic palliation only.

Unlikely.: Barbituates are not commonly prescribed in psychiatry these days, and are not a treatment for schizophrenia. Catatonic schizophrenia would be treated with antipsychotic medications, although in an acute situation a single dose of a benzodiazepine might be indicated as well.