Tempest Strike Spell Scaling Fluctuations

Tempest Strike scaling fluctuations

If i have a staff with -3 reduced spell cost the mana reduction only applies 1 out of 3 hits
(I don’t have any of the passives to remove any of the spell strikes)

screenshot timeline:
https://imgur.com/a/9XtmQ1R

From what I gather only the Frigid Tempest is applying the spell scaling effect whereas Wind Tempest and Thunder Tempest does not apply the spell scaling effect though I have only tested for mana reduction.

This doesn’t feel like it is intended but I could be wrong.

Thanks

-Goblix