TextField not updating until another TextField is updated

I'm encountering an issue with SwiftUI where a TextField does not update immediately when text is entered. Instead, the update only appears after another TextField is updated. I'm using @State variables to manage the text for each TextField.

import SwiftUI

struct ContentView: View {
    @State private var amount = ""
    
    var body: some View {
        VStack{
            TextField("inputNumber", text: $amount)
                .foregroundColor(amount.count < 10 ? .red : .primary)
            
            TextField("inputNumber", text: $amount)
                .foregroundColor(amount.count < 10 ? .red : .primary)
        }
    }

}

the issue

AFAIK, a TextField does not refresh when it is in focus.

A workaround is to use another var, as shown in the example code.

struct ContentView: View {
    @State private var amount = ""
    @State private var color = Color.primary // <-- here
    
    var body: some View {
        VStack{
            TextField("inputNumber", text: $amount)
                .foregroundColor(color) // <-- here
                .onChange(of: amount) {
                    color = amount.count < 10 ? .red : .primary  // <-- here
                }
        }
    }
}