Blood magic and cluster jewel with mana reservation efficiency

Hi I am using blood magic in standard and a small cluster jewel with pure might (purity of fire has 80% mana reservation efficiency)
As I can see here: https://pathofexile.fandom.com/wiki/Blood_Magic

The cost of skills is calculated normally, so reduced mana cost or reduced mana reservation modifiers will reduce the amount of life used.

Unfortunately nothing happens, the reservation of life (instead of mana) is still the same. So I have no advantage of the pure might in combination with blood magic.

Is this a bug? How can I reduce my aura reserved life cost?

Reduced mana reservation anything only affects mana reservation. If you're reserving life, none of that does anything anymore.
Reduced mana cost will not do anything either. Reduced cost will, but not reduced mana cost. Reduced cost doesn't affect reservation either.