Earlier quoted context omitted.
I see your point but as long as the 1. You only get notifications for numbers you sign up to watch 2. The webhook only notifies me that will be transferred (using some data format) then it shouldn't be a problem, should it?
I think it would be ok as long as it didn't tell you what the person's new number is or who now owns if it gets reassigned.
We just wanted to know so that we wouldn't charge the new owner for things the old owner ordered etc.