SwiftUI FormStyle has no insetGrouped member

I'm trying to use the new .formStyle(.insetGrouped), as mentioned in the WWDC 2022 presentation "What's new in AppKit". However, I don't see it in the documentation for FormStyle, and the following code below fails to compile because it's not a member:

import AppKit
import SwiftUI
import PlaygroundSupport

struct ContentView: View {
    @State var text = ""
    @State var toggle = false
    
    var body: some View {
        Form {
            TextField("Text", text: $text)
            Toggle("Toggle", isOn: $toggle)
        }
        .formStyle(.insetGrouped)
    }
}

PlaygroundPage.current.setLiveView(ContentView())

Am I missing something here (i.e. declaring some SDK version)?