Onix's Harden attack, where does the effect reside? Rulebook conflict

[ShadowCard]

During your opponent's next turn, if Onix would be damaged by an attack, prevent that attack's damage done to Onix if that damage is 40 or less

The wording hints the effect is on Onix. The Compedium lvX has this entry for Harden:

Harden (Cascoon - Diamond and Pearl; Silcoon - Diamond and Pearl; Graveler - Legendary Collection; Others)
Q. If I use Cascoon's "Harden" attack which prevents any attack damage that is 30 or less during the opponent's next turn, does that come before or after calculating for Weakness/Resistance?
A. Weakness & Resistance are factored in before determining whether Harden blocks it or not. So if a fire Pokémon's attack does 20 damage to Casoon and then +20 more is added for Cascoon's Weakness, Harden would not prevent the damage. (May 31, 2007 PUI Rules Team)

Since Harden looks at the damage AFTER W/R is applied, Harden's effect is on Onix, which would be the Defending Pokemon on the opponent's turn. However, the Stormfront rulebook on page 19 puts Harden at step b:

"Figure out damage effects on the Attacking Pokemon (for example, Onix's Harden attack from the opponent's turn). Then, if the base damage is 0 ..."

Step b is also before the two steps where you increase/decrease damage for weakness and resistance.

Based on the compendium entry, Harden's effect should be on the Defending Pokemon (Onix) and not the Attacking Pokemon, so it shouldn't be an example of a step b damage effect. It should belong in step f "apply any relevant effects on the defending Pokemon, resulting from the Defending Pokemon's last attack (for example, Empoleon's Steel Wing) or relevant Poke-Powers and Poke-Bodies."

Rulebook mistake?

 

[PokePop]

Sounds like it.
We'll discuss it with PUI