I went and found the certificate and it does say ‘Citizenship’ instead of ‘Naturalization’.
Reading into the document is interesting though and I am going to try to post a picture do you can see it but it says;
‘... is now a US citizen...’ which I contend it would not if I was previously a US citizen.
I am unable at this time to get FR to let me paste some lines or a picture. I will try to get that figured out.
Previously, you were an unregistered "citizen-at-birth". Had you died between the time of your birth and the time of your registration, you were still an American "citizen-at-birth" and would've been buried as such.