If "Set numbering value" uses hidden text, there appears to be a difference in the Word 2010 and Word 2013.

Modify the Style of Heading 1,2,and/or 3 | Format Button | Numbering | choose a Numbering Format | OK button.

In the document, if I adjust the Number for a paragraph - with Style Heading #|
Choose ONLY the Number on the paragraph - Right Click "Set numbering value"
Prompt for "Changing the number format for this list updates the style "Heading 2" and reapplies the style to each paragraph. Do you want to continue?" Yes button

With Show/Hide set to Show in Word 2013 - I see the additional empty paragraphs above the paragraph I set the value on.
In Word 2010, the empty paragraphs do not appear.

Undocumented feature?