pageControl hidden when pageCurl forward

I have a simple setup.

A PageViewController, with ghorizontral navigation and Page Curl defined in IB

3 UIViewControllers, with storyboard ID as Page1, Page2, Page3

On each, just a label with the Page x content and a UIImageView with colored background

In PageViewController, I define a pageControl programmatically (could not find how to define in IB).

Then, as soon as I start swiping to turn from initial page (e.g., 1) to next page (e.g., 2), pageControl hides on initial page (1) and appears on the new page (2), with the old value (the one of page 1). Idem form 2 to 3.

However, when I swipe to return from a page (e.g., 2) to previous page (e.g., 1), pageControl remains visible on page 2, not visible on page 1 until turning page has completed.

Just as if during a transition, pageControl moved (with its present value) to the page beneath.

Is it intended behavior ? Why different for forward or reverse swipe ?

I tried setting

pageControl.defersCurrentPageDisplay = false

with no effect.

Here is the code for the PageViewController.

import UIKit

class PageViewController: UIPageViewController, UIPageViewControllerDelegate, UIPageViewControllerDataSource {

    let lightGray = UIColor(red: 0.9, green: 0.9, blue: 0.9, alpha: 1.0)
   
    var pageControl = UIPageControl()

    func newVc(viewControllerID: String) -> UIViewController {
        return storyboard!.instantiateViewController(withIdentifier: viewControllerID)
    }
   
    lazy var orderedViewControllers: [UIViewController] = {
        return [self.newVc(viewControllerID: "Page1"),
                self.newVc(viewControllerID: "Page2"),
                self.newVc(viewControllerID: "Page3")]
    }()
   
    var currentlyShowingIndex = 0
   
    override func viewDidLoad() {
        super.viewDidLoad()

        let childControllers: [UIViewController] = [orderedViewControllers.first!]
       
        self.setViewControllers(childControllers, direction: .forward, animated: false, completion: nil)
       
        self.view.frame = self.view.bounds
       
        self.dataSource = self
        self.delegate = self
        configurePageControl()
    }
   

    func configurePageControl() {
       
        pageControl = UIPageControl(frame: CGRect(x: 0,y: UIScreen.main.bounds.maxY - 50,width: UIScreen.main.bounds.width,height: 50))
        self.pageControl.numberOfPages = orderedViewControllers.count
        self.pageControl.currentPage = 0
        self.pageControl.tintColor = UIColor.black
        self.pageControl.pageIndicatorTintColor = lightGray // UIColor.gray
        self.pageControl.currentPageIndicatorTintColor = UIColor.green
          //        self.pageControl.defersCurrentPageDisplay = false     // This has no effect
        self.view.addSubview(pageControl)
    }
   
    // MARK: Delegate functions
   
    func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {

        let pageContentViewController = pageViewController.viewControllers![0]
        self.pageControl.currentPage = orderedViewControllers.index(of: pageContentViewController)!
        switch self.pageControl.currentPage {
        case 0: self.pageControl.currentPageIndicatorTintColor = .green
        case 1: self.pageControl.currentPageIndicatorTintColor = .orange
        case 2: self.pageControl.currentPageIndicatorTintColor = .red
        default: self.pageControl.currentPageIndicatorTintColor = lightGray // .gray
        }
       
    }

    func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
       
        guard let viewControllerIndex = orderedViewControllers.index(of: viewController) else {
            return nil
        }
        let previousIndex = viewControllerIndex - 1
        guard previousIndex >= 0 else {
            return nil
        }
        guard orderedViewControllers.count > previousIndex else {
            return nil
        }
        currentlyShowingIndex -= 1
       
        return orderedViewControllers[previousIndex]
    }
   
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
       
        guard let viewControllerIndex = orderedViewControllers.index(of: viewController) else {
            return nil
        }
        let nextIndex = viewControllerIndex + 1
        let orderedViewControllersCount = orderedViewControllers.count
        guard orderedViewControllersCount != nextIndex else {
            return nil
        }
        guard orderedViewControllersCount > nextIndex else {
            return nil
        }
        currentlyShowingIndex += 1
       
        return orderedViewControllers[nextIndex]
    }
   
    func viewController(at index: Int) -> UIViewController {
        return orderedViewControllers[index]
    }
   
    func presentationIndex(for pageViewController: UIPageViewController) -> Int {
        return currentlyShowingIndex
    }
   
    func presentationCount(for pageViewController: UIPageViewController) -> Int {
        return orderedViewControllers.count
    }

}