You are not guaranteed to have your layout preserved when printing. This can be for a variety of reasons, but it could be simple stuff like having your file in A4-format and your printer only having papers of type "Letter" or something equally silly. In cases like these, Word is forced to reformat.
If you need or rely on a 100% accurate re-representation of your content, Word should not be your tool. Never. Use PDFs. Simple as that. If you are writing a normal texts however, it will probably never be a real problem which you will even notice.
Now, my question to the author (should he check out HN): How on earth is this related to OOXML? Where is the smoking gun saying this is a bug in the file-format? I honestly don't see it, and I don't see anyone else here questioning this unbacked claim.
I honestly expected better from HN.