Potentials could be a subset of stalk-rescued infants. If you assume that "normal" unplugged Zionists are former hackers (something that a young child, like a Potential, is unlikely to be) another source of humans with plugs would be the fields. There may be a regular concerted effort to rescue children from the fields... prepared to be plugged in but not quite yet. If they grow up with the knowledge of the Matrix, it's possible that's why some of their powers are greater than average.

Objections

If you don't buy that as a source of Potentials, the alternative bolsters the possibility that plugged people still exhibit signs of bending as per "World Record" and several comics. If the Potentials were specifically recruited (a rational assumption considering the effort and dangers involved in rescue and rebuilding) then it stands to reason that they exhibited some sign of their potential other than hacking.

Of course, there's always the alternative view that freedom is only for middle-class or better people who can afford computers and have the luxury of time for hacking (that is ONLY hackers are free) and that some of the Potentials have been hacking since they've been in diapers. A belief this site does not subscribe to.