There is a genuine dispute of material legal issues about his status at the time of birth and the effect of his foreign citizenship.
The original purpose for NBC was a heightened loyalty to America, greater than naturalization, which purpose may have been legally compromised by his foreign citizenship even if he was a NBC at birth. Both his NBC status at birth and his Canadian citizenship are material legal issues which need resolution in a federal court.
I wouldn't say "heightened," but undivided. There is another aspect too. A dual citizen is subject to the jurisdiction of two countries, meaning "the other" country can arrest, charge, press into service, tax, extradite, and otherwise do the things that countries do to citizens.