Powell never has been officially part of the team. The team is just pointing this out. If anything, the team is clarifying this because of what's about to come out. They need to make clear to the public that there aren't any conflicts of interest or anything like that.
All that said, nothing stops Powell from working with the actual legal team, which is what she's been doing the whole time.
That's CSPAN labeling her that way and they probably did it because Trump said she was part of the team, but that doesn't mean that she actually is. She said herself that she's representing the people.
I really don't read it as a recent decision that was made, but simply the way it already was and it's just being clarified.
Maybe getting the information out and on record so that it can be used elsewhere is her true role.
Anon, I'm going to have to ask you to suspend judgment and trust the plan. Powell's not out of the equation.