Burning Inscription/Decaying Hex not scaling with increased damage.

Title.

% increased damage seems to have no effect in the damage dealt by either of these support gems. Burning inscription for example has the wording "Create Ignited Ground, Igniting enemies as though dealing 20% of your maximum mana"

In contrast, solar Orb or flame wall have "Ignites as though dealing x to x damage". In theory both of them should scale with % increased fire damage, but only the active skills scale, and the support gem does not. It feels weird to have a support that looks really fun to use, but just doesnt work for some reason that is not even stated clearly. Like at least mention that it is unscalable damage similar to the wording of Herald of Blood. But actually maybe dont do that and just let it scale instead?