[DavidTrap (David)]

I think you're technically right, but I recall reading somewhere that if you have the base level, it isolates interactions between azimuth and altitude when doing polar alignment. Old fashion drift alignment is easier if you can correct for azimuth when pointing up and altitude when pointing to the horizon. My guess is that it is also easier for the "computer aided" polar alignment routines that many use with the mounts you mentioned above. These routines usually say to turn the azimuth & altitude knobs so far - I would expect that the software is assuming the pier top is level when making those calculation??? (Although, I also have vague recollections of a recent thread that may have mentioned the Paramount software being able to cope with it being out of square too?)

DT