Several of the Barbarian Instinct Abilities modify the traits of the Rage action.
Draconic Rage (Instinct Ability)
While raging, you can increase the additional damage from Rage from 2 to 4 and change its damage type to match that of your dragon’s breath weapon instead of the damage type for your weapon or unarmed attack. If you do this, your Rage action gains the arcane and evocation traits, as well as the trait matching the damage type.
As well, the arcane trait only seems to indicate the effect is magical in nature:
arcane (trait) This magic comes from the arcane tradition, which is built on logic and rationality. Anything with this trait is magical. 299
What mechanics in the game (if any) interact with this modification of the Rage action?
Rage isn't a spell, so it can't be dispelled. Antimagic field doesn't seem to interact with abilities such as this. Rage mainly just modifies weapon damage, so its not like resistance is interacting with the traits of Rage, but rather its modified damage type. Other class Feats tied to the instinct that might have saves (e.g. the dragon's breath) have the traits, and it makes sense in that context.