Charged Staff Doesn't benefit from Increased Duration

Charged staff doesn't appear to get any bonus from increased duration (which seems unintended as it's quality effect is increased skill effect duration), it is 6 seconds per power charge no matter what. It's possible that it is because my charged staff gem is corrupted with 3% quality and that is bugging it somehow. Regardless, even with 20% increased duration from passives it still seems to only get 6 seconds per charge consumed.

Edit: Appears to be a tooltip error? I am able to get it to 36 s duration with 5 power charges despite it saying 6s per power charge. It was harder to tell how much it was benefiting when only consuming 1 charge. Changed tag to Text.

Sorry if dupe, didn't see any other posts about this.

I also noticed that increased duration is not effecting Charged Staff. The Persistence support gem does nothing for the skill even though it shows as one of the 3 options for skill on lvl 1 uncut support gem.