TBH... You had peaked my curiosity with this question... LOL!
I had done a bit of looking around on both Ancestry.com and FamilySearch.org.
My deduction is "Yes". I believe that their one in the same.
Based upon my findings, this individuals real name is "Nicholas DePuy Decker" (the middle name came from his mother's maiden surname).
It does looks like Nicholas had decided to use a different name, possibly, when he had enlisted in the Revolutionary War.
It doesn't look like his last name change fell into the "legal" realm, but back then (years ago) this type of sporadic change in names were not an uncommon occurrence.
Actually, many years ago, an individual could go by another name just by stating/using that it's their name (sometimes after moving to a location where nobody knew him/her).
So is his last name Dix? Technically, I would safely state that the profile could reflect his last name as "Dix (formerly Decker)".
I only suggest this because I did notice some/all of his children were, apparently, born with the last name of "Dix".
I hope I had explained the above okay via text and is ONLY based upon my personal findings without getting too in depth with the search. I always welcome any rebuttals/discussion regarding this topic.
Good Luck! :-)