No reason, really. Greta is just the first person that flashed to mind with integrity.
She’s serious and professional and I think she would go out of her way to be unbiased.
I sincerely can’t think of many people with great integrity. Can you?
I see a few good suggestions upthread between my last post to you and your last post. I wasn’t putting the suggestion out there as a challenge to your choice of Greta. I think she has the integrity and she is also tough enough and diplomatic enough to impose discipline on the participants. She has good interrogative skills too.