Suggestion

Since IIngredientSubtypeInterpreter has been deprecated for removal, the interface ISubtypeInterpreter<T> is recommended to be used instead. However, that interface also defines a method (getLegacyStringSubtypeInfo) that is deprecated for removal and does not provide a default implementation that e.g. calls the other method. With only one abstract method, the interface could be a functional one, too.

Thanks for the report!
This is a necessary part of updating the API without breaking changes.
Methods are added and removed slowly over time in order to keep backward compatibility and provide a safe way forward.
To maximize compatibility, please continue to implement methods until they are removed in later versions.