任意属性那个章节运行的效果和教程不同

[suzhenghui-sky]

https://ts.xcatliu.com/basics/type-of-object-interfaces.html
interface Person {
name: string;
age?: number;
}

let tom: Person = {
name: 'Tom',
age: 25,
gender: 'male'
};
我运行了不报错。
ts 编译器版本：Version 4.5.5