YANG parser does not complain about invalid enum default after refining enum

We are using version 2.0.11.

According to the YANG RFC https://tools.ietf.org/html/rfc7950#section-7.3.4 :

   If the type's default value is not valid according to the new
   restrictions specified in a derived type or leaf definition, the
   derived type or leaf definition MUST specify a new default value
   compatible with the restrictions.

The YANG parser does not complain about this, see the example yang model attached to this ticket, which is parsed without error.

For the same YANG model, pyang reports the following error:
example.yang:16: error: the value "one" does not match its base type - enum not defined for the default value