Section(isExpanded:) in sidebar List, inconsistent row animation on collapse/expand

When using Section(_:isExpanded:) inside a List with .listStyle(.sidebar) in a NavigationSplitView, some rows don't animate with the others during collapse and expand. Specific rows (often in the middle of the section) snap in/out instantly while the rest animate smoothly.

I've reproduced this with both static views and ForEach.

Minimal reproduction:

struct SidebarView: View {
    @State private var sectionExpanded = true
    @State private var selection: Int?

    var body: some View {
        NavigationSplitView {
            List(selection: $selection) {
                Section("Section", isExpanded: $sectionExpanded) {
                    ForEach(1...3, id: \.self) { index in
                        NavigationLink(value: index) {
                            Label("Item \(index)", systemImage: "\(index).circle")
                        }
                    }
                }
            }
            .listStyle(.sidebar)
            .navigationTitle("Sidebar")
        } detail: {
            if let selection {
                Text("Selected item \(selection)")
            } else {
                Text("Select an item")
            }
        }
    }
}

Environment: macOS 26.3, Xcode 26.3, SwiftUI

Steps to reproduce:

1. Run the above code in a macOS app
2. Click the section disclosure chevron to collapse
3. Observe that some rows animate out while others snap instantly
4. Expand again — same inconsistency

Expected: All rows animate together uniformly.

Actual: Some rows (typically middle items) skip the animation entirely.

I also tried using static Label views instead of ForEach, same result. Is there a known workaround?