If user has ability to show icon, it is never told that actually the string he/she writes is class name. But why it made such way? Because of any other way it takes somebody to maintain huge mappings.
Enabled/disabled is condition brought to be controlled at the user level. If it is also the class name, coincident, but not always the case.
All those help the dashboard from one or other side to be easy to use but still provide plenty of options to be reasonably custom.
But OK. You want to change some property for
md-card by sending message . (ignoring the fact that md-card is not the widget but container to maintain the layout)
What property and why?