A note in 5.1.1 mentions that the case of field/property hiding in hierarchies is unspecified and will be clarified in a later revision.
I guess it's too late to address this for 1.1, but if we ever will, the following rules might make sense:
In case a complete bean is validated, constraints on hidden and hiding members are evaluated (the members can be independently discovered and metadata such as constraints gathered for these)
In case a single property is validated (validateProperty, validateValue), only the hiding member gets validated (validateValue could be invoked for the supertype member separately, for validateProperty I don't see a way how the hidden member could be targeted)
The metadata API exposes the hiding member only (metadata for the hidden member could be retrieved from the supertype)