UIScrollEdgeElementContainerInteraction uses wrong mix-in color over WKWebView on iOS 26.1

There seems to be a regression in the behavior of UIScrollEdgeElementContainerInteraction on iOS 26.1 when it's over a WKWebView. If the web view's scroll view's topEdgeEffect.style is changed to .hard and then back to .soft, it will stop tracking the color of the content underneath it and use the wrong-mix in color in its blur.

I've filed this as FB20655398.

Here's some sample code to illustrate the issue. The test.html file being loaded is just a bunch of div elements with lorem ipsum.

    private var webView: WKWebView? = nil
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let config = WKWebViewConfiguration()
        let webView = WKWebView(frame: .zero, configuration: config)
        webView.navigationDelegate = self
        self.view.addSubview(webView)
        webView.autoPinEdgesToSuperviewEdges()
        webView.isInspectable = true
        self.webView = webView
        
        let url = Bundle.main.url(forResource: "test", withExtension: "html")!
        webView.loadFileURL(url, allowingReadAccessTo: Bundle.main.bundleURL)
        
        let blurView = UIView()
        self.view.addSubview(blurView)
        blurView.autoPinEdgesToSuperviewEdges(with: .zero, excludingEdge: .bottom)
        
        let label = UILabel()
        label.text = "This is a title bar"
        blurView.addSubview(label)
        label.autoAlignAxis(toSuperviewAxis: .vertical)
        label.autoPinEdge(toSuperviewEdge: .bottom, withInset: 8)
        label.autoPinEdge(toSuperviewSafeArea: .top, withInset: 8)
        
        let interaction = UIScrollEdgeElementContainerInteraction()
        interaction.scrollView = webView.scrollView
        interaction.edge = .top
        blurView.addInteraction(interaction)
        
        self.webView?.scrollView.topEdgeEffect.style = .hard
        
        DispatchQueue.main.asyncAfterUnsafe(deadline: .now() + .seconds(2)) {
            self.webView?.scrollView.topEdgeEffect.style = .soft
        }
        
        registerForTraitChanges([UITraitUserInterfaceStyle.self]) { (self: Self, previousTraitCollection: UITraitCollection) in
            self._updateWebViewColors()
        }
    }
    
    private func _updateWebViewColors() {
        let dark = self.traitCollection.userInterfaceStyle == .dark
        let text = dark ? "#FFFFFF" : "#000000"
        let bg = dark ? "#000000" : "#FFFFFF"
        let js = "document.body.style.color = '\(text)';\ndocument.body.style.backgroundColor = '\(bg)';"
        self.webView?.evaluateJavaScript(js) { res, err in
            if let err {
                print("JS error: \(err)")
            }
        }
    }

If you run that, then change the system them to dark mode, you get this. Has anyone else seen this before? Know how to work around it?