Apposition (as a relation) and coordination as defined in the sources you cite deal with MEANING.
But whatever the drawbacks of those definitions might be, we here spoke not of RELATIONS, but of GRAMMATUCAL CONSTRUCTION the definition of which you referred to in the wikipedia article and which is described in the sources I cited.
So you still don't see how you are contradicting yourself and the cited materials?

Modification is not a subset of apposition, nor are they synonymous.