I hear that statement time and time again, it is so wrong, most 'experts' say that because they do not or cannot grid and fit the shims (lash caps if you are American) or they have hydraulic cams in stock and want to sell those.
One of the best modifications you can do to the YB especially if high power and more boost.
Costs more money, extra labour to sort the shims, solid lifters, shims, but the cams are similar money.

Steve