Class by Handle should inherit from MMgt_TShared??

I always thought that all class that can be manipulated by handle should inherit from MMgt_TShared. Then when I subclass the class TDocStd_Application I realized that this class doesn't inherit from MMgt_TShared and it is manipulated by handle (see the example in OCAF User's Guide section 4.2.1, and have a look at the include file). Then I look back in the manual Programming Samples Volume I (version 2.1), where it says that handle are used with objects inheriting from MMgt_TShared (page 2-3, 2-4). And then, in the Foundation Classes User's Guide (for version 3.0, page 25) it says that in order to benefit from the memory manager and reference counter (which is the handle), class should inherit from Standard_Transient...

So now, in version 3.0 we should inherit future handle manupilated class from Standard_Transient?? Why this has changed?? It doesn't cause any problem, I'm just curious... Thanks you. Francois.