I don't see why you wouldn't be able to tap it, unless as you say tim just doesn't do it anymore.
I nearly got into an argument with the guys in Music Ground on Denmark Street a while ago about a Gordon Smith with p90's, they were saying that they used the same push-pull pots on all their guitars, but they weren't wired in on the p90 models since you couldn't tap a single coil/p90. I tried to explain that single coil meant you couldn't split but could still tap, but gave up eventually and just went back to trying out the damn thing, which was what I was there for!
Moral- listen to what Tim says, not the guys at your guitar shop.
:drink: