Could it be? Yes, if that ability were added in the core code.
Will it be? Almost certainly No, because the point of making the availability restrictions as a plugin based tool was so that it could be easily extended by plugins that add specific types of restrictions. That means such additional restriction types would be unlikely to be added to core code.
The proper way to do it would be make a new restriction type plugin modeled on the course role one to instead use course enrollment type as the criterion.