Now, normally you can only Complete a Job by forming a team from cards in your hand and playing that team into Night One. All I see the Underboss ability allowing is that a team can be formed from cards in your Refresh Area as well as from cards in your hand.
As far as I can tell, there's no reason to think the Underboss ability does any more than that, like changing the rules about the type of skills required to complete a job.
If that's right, I think the wording could be clarified by simply dropping the "any"; as in:
Improved wording of Underboss ability wrote:
"You may Complete a Job this turn using
any cards in your hand and/or Refresh Area. (The Underboss does not count toward this job."
This change would help emphasise that the Underboss ability is about where
you draw cards from, not which
cards you can use, to Complete a Job.