The STIX 2.1 spec says:
An object using the Windows™ PE Binary File Extension MUST contain at least one property other than the required pe_type property from this extension.
WindowsPEBinaryExt only gets the default at-least-one property presence check (any property). It needs to ensure that at least one property is present other than pe_type.
The STIX 2.1 spec says:
WindowsPEBinaryExtonly gets the default at-least-one property presence check (any property). It needs to ensure that at least one property is present other thanpe_type.