SwiftUI - Text minimumScaleFactor not scaling only when needed

Adding .lineLimit(1) to the Text will work well.

Xcode: 11.3.1

Adding a GeometryReader around the VStack that my two Text views were in solved this. As requested by @gohnjanotis:

GeometryReader { proxy in
    VStack(alignment: .center, spacing: 0) {
        HStack {
            Image("medal \(self.place)").resizable()
                .foregroundColor(self.color)
                .frame(width: 40, height: 40)

            Spacer()
            Text(self.username)
                .minimumScaleFactor(0.1)
                .font(.bold(16))
                .lineLimit(1)
                .frame(alignment: .trailing)
                .foregroundColor(Color("mediumTextColor"))
                .layoutPriority(1)

        }
        .padding(.top, 10)
        .padding(.horizontal, 10)
        Spacer()
        Text(self.score)
            .font(.extraBold(60))
            .foregroundColor(self.color)
            .lineLimit(1)
            .minimumScaleFactor(0.1)
            .layoutPriority(1)
            .padding(.horizontal, 10)
            .padding(.bottom, 10)
            .offset(y: -10)
    }
    .frame(width: proxy.size.width, height: proxy.size.height, alignment: .top)
}
.frame(maxHeight: 130)

A continuation of answer above.

What is important is the order in which the modifiers are applied:

Text("This is a really long sentence.") 
   .minimumScaleFactor(0.5)                
   .font(.custom("OpenSans", size: 15))
   .lineLimit(1)
   .layoutPriority(1)

There isn't a need for the GeometryReader unless you need it for something else

Important for that minimumScaleFactor() only does its job when it is needed, is the combination of .minimumScaleFactor AND .lineLimit(1); otherwise it will not work. layoutPriority(1) is not the key here.

Example - this works; Scale is only applied when needed:

Text("Something").minimumScaleFactor(0.5).lineLimit(1)