The documentation for Sacred Gold/Storm Silver serves three vital functions:

: You don't need to trade to get a Gengar or Alakazam. This document explains how new items like the Covenant Orb or Voltaic Ore let you evolve trade-only Pokémon simply by "using" the item from your bag.

: Lists modifications to base stats, types, abilities, and level-up movepools. For example, some Pokémon have been granted secondary typings or had their competitive viability boosted via increased Attack or Speed stats. Important Trainer Teams