Those 1up hands-on reports seem fishy to me. Dualshock rumble was stereo also. That's what the word dual meant.
The dualshock motors were widely underutilized. Compare the rumble in Metal Gear Solid, such as when the helicopter is taking off, to all the games that use the rumble just to have the controller shake at maximum strength whenever there's an explosion on-screen.
However, it would be possible to get more subtle rumble with the same motors if you could vary the current going into them-though if one had this there would no reason to use asymmetric motors anymore, so you wouldn't use the same pair of motors.