Typescript type returned by getFields()

[IanVS]

I'm wondering if the typescript types for getFields() is correct, because it is defined as returning this:

export type GraphQLFieldMap<
  TSource,
  TContext,
  TArgs = { [key: string]: any }
> = {
  [key: string]: GraphQLField<TSource, TContext, TArgs>;
};

Which means that type.getFields().foobar will always be treated as truthy, even if no such field exists in the schema, right? I feel like maybe I'm missing something, but I would have expected to get back something more like:

export type GraphQLFieldMap<
  TSource,
  TContext,
  TArgs = { [key: string]: any }
> = {
  [key: string]: GraphQLField<TSource, TContext, TArgs> | undefined;
};

Is this an issue, or something I'm misunderstanding?