> this makes sense—technically both the offset of the Central Directory and the size of the Central Directory are redundant when you consider that the End of Central Directory Record should be, well, at the end of the Central Directory. In a proper ZIP file the following equation should be true: (position_of_EoCDR - size_of_CD == offset_of_CD)

This is a pretty clear statement on normativity.

You also left out an important part of my comment when you quoted it. (The operative word at the front of the sentence is "seems".)