Should UIScrollEdgeElementContainerInteraction work with a WKWebView's scroll view?

In iOS 26 beta 3, it was possible to have a UIScrollEdgeElementContainerInteraction work with a WKWebView's scroll view. But it stopped working in beta 4, and is still broken in beta 5 today. Is this expected? Or is this a bug that will be fixed before public release?

Filed as FB19386650 with a trivial sample app.

I also experienced strange edge effects on macOS when mixing AppKit and SwiftUI. The scroll edge always appears dark, even in light mode. This worked well in beta 5 with Xcode Beta 5, but it persists in beta 6 and 7.

The following screenshot was built with Xcode beta 7 on Tahoe 7, and I still got the issue.

Should UIScrollEdgeElementContainerInteraction work with a WKWebView's scroll view?
 
 
Q