I think the most down to earth example is the AST or data protocol examples. Take Jason for example. Instead of having a JsonValue class to hold the data you would have a Union type that is either string, bool, number, array of your union type or map type which uses a string as key and the same union type as value. It would also allow to implement result types like rust has them. So you could define an API that returns a value or an error. I didn’t see in the proposal if they talked about generics though. In functional programming world this is mainly known as algebraic data types. I can say that if you get used to model types like this you really start to miss it in languages that don’t support it.

[1] https://en.m.wikipedia.org/wiki/Algebraic_data_type