Formatter.Duration listed but not implemented in OmniPlan4?

Formatter.Duration appears in the OmniPlan4 API documents, but am I right in thinking that it hasn’t been implemented ?

Whereas in the case of OmniFocus we can write:

fmr = new Formatter.Duration()

//--> {hoursPerDay: 8, hoursPerWeek: 40, useVerboseFormat: false}

In OmniPlan4 the same incantation yields:

TypeError: CallbackObject is not a constructor (evaluating 'new Formatter.Duration()') undefined:1:29