Overlay vs override

Microsoft is trying to achieve consistency among all the classes in AX to have the following condition met:
Each class has construct method which takes no parameters. This constructor should be the primary entry point for class construction, e.g. any other constructor should use construct() inside.
For the same reason, to avoid direct instantiation of the objects via new() method they are marked as protected. It is done in such way because it looks like overriding is much more maintainable than overlaying. It is better to create a sub-class in the outer layer that extends super-class in inner layer and overrides the required method + have construct() method overlaid to instantiate sub-class instead. Code upgrade in this case seems to be much cheaper comparing to the case when methods are overlaid directly on the super-class.

So my question basically is, if this statement is correct or not? Are you writing code in the described way? If no, why? What are the cases when overlaying is better that overriding?