This section is a misnomer. Contrary to highlight properties, there is no inheritance for layout properties across a face tree. In other words, every missing layout property in a face specification has the property in question set to its default value.
Again, this design decision has been adopted because it is the most natural thing to do. If you’re not convinced, consider this: when you specify that the ‘option’ face has a top padding of 0, you mean that every option should be described on a line of its own. However, you probably do not mean that every individual sub-part of the option’s description (syntax part, usage part etc.) should also start on its own line.
Now that we know all about highlight and layout inheritance, we are able to explain the face specification shortcut mentioned earlier, when a face is specified directly by name, without any explicit property specification:
:face description
This syntactic shortcut actually lets you specify a face which gets all default values for layout properties, and inherits all current values from its super-faces for highlight properties. This is in fact a shortcut for this:
:face (description)
This, however, does not explain why you would want to issue such a specification instead of just not mentioning the face at all. See Implicit Faces for an explanation.