Actually he is probably right and wrong.
Lifting the rear of the truck will have an impact on the steering alignment. Imagine the steering components rotation axis.... the "upper" location of this axis - the UCA - will be further forward than the lower axis. this would change steering alignment... BUT
a lift of 1.5 - 2.0 inches on a 104" wheelbase will only change the steering axis by .55 degrees so the alignment is probably unnecessary.