TypeScript method overriding rules

Question

I'm trying to pick up some TypeScript knowledge for my work, and I just realized that the implementation of method overriding in a derived class is different from other static typed languages such as Java.

For example, I realized I can do this in TS:

class Base {
    constructor(greet: string){
        console.log('base', greet);
    }

    getExample(arg1: unknown): unknown{
        console.log('base getExample', arg1);
        return ''
    }
}

class Derived extends Base{
    constructor(){
        super('Hello');
    }

    getExample(arg1: string): string{
        console.log('derived getExample', arg1);
        return 'something'
    }

    getExample2(arg1: string): string{
        console.log('derived getExample2', arg1);
        return '2'
    }
}

const doj: Base = new Derived();
doj.getExample(123); // derived getExample 123
doj.getExample('123'); // derived getExample “123”
(doj as Derived).getExample2('123');

I'm wondering why is the getExample in the Derived class overridden not overloaded(the argument type and return type are different from the getExample in the Base class)?

I can't find what the rules of method overriding are in the TS handbook, hope I can get help here. Many thanks.