The OfficeAddress Style seems to be partly hard-wired in Word 2010 and 2013. I have not tested other versions.
Here is a screenshot showing the style definition in the normal template (as modified by me).
When I use the Mailings tab Envelope button to insert an envelope into the document, this is changed.
My paragraph indentation (inside the frame) is set to 0.2 inches. This is reset by Word to 2.0 inches. The frame itself is set to be oriented horizontally Left; that is reset by Word to Center.
These screen shots are from the same document, before and after use of the Envelope > Insert in document function.
I never use the Envelope button, preferring to use my own envelope templates, so I hadn't noticed this until someone on another forum complained that they couldn't get rid of the 2" indent. I told them to change the EnvelopeAddress style. They did and that did not help, so I tried it myself in both Word 2010 and 2013. The only things I tried changing were the indentation and frame position. The person who asked me about it reported that some things could be changed, but not the indentation. Here is a link to that thread. http://www.msofficeforums.com/word/29482-envelope-template-style-not-sticking.html
I suspect that many of the people answering questions here do not regularly use that function and so this was not noticed. To me, this is a bug. I don't have 2016 but suspect it is there as well.