SMETS and CHTS require that the Critical Commands mandated by them (and so those defined in the GBCS) are the only Critical commands allowed. Devices may implement additional non Critical features only.
SMETS and CHTS only require DLMS COSEM support on the ESME.
DLMS COSEM objects (or functionality equivalent to them) are required to deliver the ESME functionality defined in the Use Cases in a consistent way but should not be accessible via the ESME’s HAN interface (i.e. it is internal functionality).