Get wrong fromController using custom transition

I did a custom transition between ViewControllerA and ViewControllerB. But the fromVc type is not ViewControllerA. (I debug found it is a Tab Controller)

I want the fromVC to be ViewControllerA, or I can get ViewControllerA somehow. (I also use transitionContext.viewController(forKey: .from)?.children.last or first, still not working)

In ViewControllerA:

extension ViewControllerA: UIViewControllerTransitioningDelegate {
func animationController(forPresented presented: UIViewController,
                             presenting: UIViewController,
                             source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        if presented is ViewControllerB {
            return Animator()
        }
        return nil
    }

// here is how I present ViewControllerB in ViewControllerA's viewModel

let vcB = ViewControllerB()
vcB.transitioningDelegate = delegate
vcB.modalPresentationStyle = .custom
self.delegate.present(vcB, animated: true, completion: nil)

in ViewControllerB: nothing special

in Aminator

public class Animator: NSObject, UIViewControllerAnimatedTransitioning {
    public func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 3
    }
    
    public func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        // I need to do some staff in ViewControllerA so that I need to get fromVc.
        guard 
          fromVc = transitionContext.viewController(forKey: .from)? as ViewControllerA, 
          toVc = transtionContext.viewController(forKEy: .to)? as ViewControllerB else {return}
        // do some animation in CATransaction and settransitionContext.completeTransition(true)
        // ....
    }
}