insert(classObject) for SwiftData add & update, both?

Very simple SwiftUI/SwiftData app below to demonstrate concepts. I've been using the same DetailView to handle add & update in SwiftData. Using modelConext.insert(person) seems to handle BOTH additions of a new record AND updating of the existing record without any problem. Is there any reason not to use this approach in a simple app like this? Minimalist UI below just to get to the modelContext.insert point:

import SwiftUI
import SwiftData

@Model
class Person {
    var first: String
    var last: String
    init(first: String = "", last: String = "") {
        self.first = first
        self.last = last
    }
}

struct DetailView: View {
    @State var person: Person
    @State private var first = ""
    @State private var last = ""
    @Environment(\.dismiss) private var dismiss
    @Environment(\.modelContext) var modelContext
    var body: some View {
        VStack {
            TextField("first", text: $first)
            TextField("last", text: $last)
            HStack {
                Button("Cancel") {
                    dismiss()
                }
                Button("Save") {
                    person.first = first
                    person.last = last
                    modelContext.insert(person)
                    dismiss()
                }
            }
            Spacer()
        }
        .onAppear() {
            first = person.first
            last = person.last
        }
        .padding()
        .textFieldStyle(.roundedBorder)
    }
}

struct ContentView: View {
    @Query var people: [Person]
    @State private var sheetIsPresented = false
    @Environment(\.modelContext) var modelContext
    var body: some View {
        NavigationStack {
            Button("Add") {
                print("Link clicked!")
                sheetIsPresented.toggle()
            }
            List {
                ForEach(people) { person in
                    NavigationLink {
                        DetailView(person: person)
                    } label: {
                        Text("\(person.last), \(person.first)")
                    }
                }
            }
            .listStyle(.plain)
            Spacer()
        }
        .sheet(isPresented: $sheetIsPresented) {
            NavigationStack {
                DetailView(person: Person())
            }
        }
    }
}

#Preview {
    ContentView()
        .modelContainer(for: Person.self, inMemory: true)
}

AutoSave is on, but BTW I frequently add save code after, just to push changes out to watch updates in DB Browser in real-time (which the simulator doesn't seem to push & may otherwise loose if you quit before doing one of the "save-pushing" tasks like swiping to another app. e.g. follow the modelContext.insert(person) with:

guard let _ = try? modelContext.save() else {
    print("😡 ERROR: Save on DetailView did not work.")
    return
}

Thanks!