Question about Blessed Hammer

Hi to all.
I’ve notices that +2 to Vigor from Tearhaunch Greaves does not increase damage of BH.
I made some tests and it seems level of Vigor has no impact to BH damage at all.
Is it a bug, or nerf?
BTW: in BH description Vigor still marks as a synergy which gives 14% dmg per lvl.

Synergies apply only from hard points (ie. when you put a skill point).

+x skills from items will not increase the synergy.

Thank you for explanation =)