Hi Ralph,
Good observation. It is possible that it is the same person, however Pierre Guillaume has his own entry in Stephen White's Dictionnaire, p. 782. White likely did not have enough sources to believe that he could be the other Pierre. He is listed alone, no parents, spouse or children mentioned, only his name and age recorded in the 1686 census. Nothing more is known about him. If you wish, you could create a profile for him, and add a research note with your hypothesis. Birth would be in France, marked uncertain. The citation for White's Dictionnaire: Stephen A. White, Dictionnaire généalogique des familles acadiennes. (Moncton, N.-B.: Centre d'études acadiennes, Université de Moncton, 1999), Print. p. 782. Pierre Guillaume, born around 1726. On 1686 census at Port-Royal, age 60, alone.
Thanks for everything that you do, Ralph. Your steady contributions help improve the quality and accuracy of information in Acadian profiles.