The short answer is that yes, you can wire walk with Salvador's tip. As John said, it is a slow walk. So be patient with the top: if you pull too hard you are going to bind it and kill the spin or make it gyro. With a lighter pull the loop will be more open and higher, away from the narrower part of the neck.
The reason I think is two fold. As John said the surface contact area is smaller and there is less friction. More importantly, the torque applied by the string depends on the distance to the axis of rotation, which is smaller (this also affects the apparent friction seen by the top). The tip is good for regenerations because the lower friction decreases the losses in the non-regen parts of a trick.