I don't know how everybody does it, but the reason I put a witness on the list is that I have spoken to them and they are prepared to testify. So they're waiting for you to call them, since I'm not the one who issues the official summons, it's you. If the witnesses aren't waiting to be summoned, I imagine that's not as bad, but if that's the case, it's not an ideal solution.
I see that a number of witnesses have asked to be summoned. Maybe they are the ones we will decide not to invite, if that's the case.