TypeScript - Less-permissive implementation of interface

index.ts

// TypeScript v 3.2.2
//
// I feel like something along the way here should fail type-checking.
//
// The interface for Repository#saveFeed takes an attribute
// with an optional `feed` property. The implementation requires the
// `feed` property, and thus - I suppose - satisfies the requirement?

type FeedInfo = {
  feed: {
    sheetId: string;
    budgetId: string;
  };
};

type IFeedInfo = {
  feed?: {
    sheetId: string;
    budgetId: string;
  };
};

interface IFeedRepository {
  saveFeed(feedInfo: IFeedInfo): void;
}

class FeedRepository implements IFeedRepository {
  saveFeed(feedInfo: FeedInfo) {
    console.log('This line will explode.' + feedInfo.feed.budgetId);
  }
}

// This is where it starts to get a little bit weird in my mind.
// Despite explicitly implementing the interface, I'm not sure that
// FeedRepository can actually be considered an implementation of
// IFeedRepository, because ...

let repo: IFeedRepository = new FeedRepository();

repo.saveFeed({});

// ... this last line explodes. This explicitly should be ok according to the 
// IFeedRepository contract, but explicitly should not be ok according
// to the FeedRepository contract. ?

tsconfig.json

{
  "compilerOptions": {
    "strict": true,
    "noEmit": true,
  },
  "files": [
    "index.ts"
  ],
}