Unable to use custom alignment with non-sibling views with animation - swiftui

Question

Goal: to have the tapped person in the ScrollView/HStack align it's centre with the other views using the explicit custom alignment, CentreScreenAlignment
Problem: currently nothing is happening when I tap on a given person.
Code:
extension HorizontalAlignment {
private enum CentreScreenAlignment: AlignmentID {
static func defaultValue(in d: ViewDimensions) -> CGFloat {
d[HorizontalAlignment.center]
}
}
static let centreScreenAlignment = HorizontalAlignment(CentreScreenAlignment.self)
}
struct ContentView: View {
#State private var centrePt: Int = 0
var body: some View {
GeometryReader { g in
VStack(alignment: .centreScreenAlignment) {
ZStack {
HStack {
Button("Cancel") {
// action
}
.padding(.leading)
Spacer()
Button("Done") {
// action
}
.padding(.trailing)
}
Button {
// action
} label: {
Image(systemName: "person.fill.badge.plus")
.coordinateSpace(name: "Add button")
.foregroundColor(.blue)
.alignmentGuide(.centreScreenAlignment) { d in
d[.centreScreenAlignment]
}
}
}
EmptyView()
.alignmentGuide(.centreScreenAlignment) { d in
d[.centreScreenAlignment]
}
ScrollView(.horizontal, showsIndicators: false) {
HStack {
ForEach(1..<10) { index in
Group {
if index == self.centrePt {
Button("Patient #\(index)") {
//
}.transition(AnyTransition.identity)
.alignmentGuide(.centreScreenAlignment) { d in
d[.centreScreenAlignment]
}
} else {
Button("Person #\(index)") {
withAnimation {
centrePt = index
print(centrePt)
}
}
.transition(AnyTransition.identity)
}
}
}
}
}.padding()
Text("Hello")
}
}
}
}
Thanks very much.