Does Mountain Rage specifically exempt itself from Powerful Build?

Question

The Goliath powerful build racial trait and the Goliath Barbarian's mountain rage offer a pair of statements that are muddling a character for one of our campaigns, so before I make a ruling I was hoping someone more knowledgeable might shine some light on this issue.

The Powerful Build ability reads, in part:

The benefits of this racial trait stack with the effects of powers, abilities, and spells that change the subject’s size category.

Mountain Rage reads, in part:

However, he does not gain additional benefits on weapon size and grapple checks, since he already has them from his powerful build ability.

Is this line from mountain rage calling itself out as a specific exception to the powerful build abilities (that is, that powerful build "shuts off" whilst the Goliath Barbarian is raging)?

• or

Is mountain rage only saying that the effects of powerful build on grapple checks and weapon size wielding do not apply, but the other effects still do, such as his ability to be one size larger for swallow whole or improved grab?

• or

Is mountain rage's use of the word "additional" calling out its size increasing effect as distinct from, say, Enlarge Person in that it won't increase the character's equipment and other size related abilities as Enlarge Person would, but the effects of the mountain rage don't otherwise subsume the effects of powerful build?

Answer 1

The common consensus on the function of mountain rage is that its increase in your size replaces your powerful build feature, as in your first alternative. That is, during a mountain rage you (assuming a typical Medium goliath) lose your pseudo-Large status per powerful build in exchange for true Large size. And then you get an extra +2 Strength above normal because reasons.

As for what the rules-as-written actually say, that would be closer to your second option there: it excepts grapple bonuses and weapon size increases from the benefits you gain from growing in size. And, from a RAW perspective, that would be the end of the story, without really caring about the bit that references powerful build. So you would gain other benefits of growing, including those that powerful build also offers, just because only grappling and weapon size were actually excepted by mountain rage. Generally speaking, rules-as-written tends to ignore things said after “since” because it doesn’t really matter why you get a particular benefit, and because it’s ambiguous and impossible to figure out what happens when those since clauses are inaccurate (for example, a stoneblessed character could count as a goliath and take the goliath barbarian substitution level without actually, ya know, having powerful build).