In spirit gem Herald of Blood, what's the mean of "Unscalable"

In spirit gem Herald of Blood, what's the mean of "Unscalable" Physical Attack Damage?

If I select the suggest support gem page of Herald of Blood, it shows many support gem that can add damage to Herald of Blood. Is there any support gem can add damage to this "Unscalable" Physical Attack Damage? Is there any skill tree can add damage to this "Unscalable" Physical Attack Damage?

Thank you.

Not dev but I can reply to this with almost 100% certainty.

There is a flat damage portion that is scaleable with supports.

There is a % of corpse life dmg that is not scaleable with support, items, or tree.

Thank you

In traditional Chinese translation, the Unscalable is translated to Independent. Maybe you can check this. In skill tree, Lay Siege is not translated correctly. Unnatural Resilience is not either.
Alva's trade is always translated to some task title.
Maybe a whole check of traditional Chinese translation is needed.