UAF13 — No Added Extensions

For Protocol it extends Class which is redundant and probably unhelpful...

since Protocol is a specialization of Block (which extends Class) this is not helpful, because one needs to know that this stereotype
would be used instead of <<Block>> (since one can not have both a generalization and specialization of a stereotype on the same element)...

Block here is the more fundamental than the metaclass Class... but neither should be specified redundantly in the model...
it is just not helpful... what would be helpful is defining the fundamental thing in the definition of the UAF elements