Types vs React.propTypes

gistfile1.md

Why (some) frontend devs don't like TypeScript because of types but writes React.propTypes ????

Dropdown.propTypes = {
    text: React.PropTypes.object.isRequired,
    children: React.PropTypes.oneOfType([
        React.PropTypes.object,
        React.PropTypes.array
    ]).isRequired,
    autoClose: React.PropTypes.bool
};

vs

function(text: string, children: Object|Array, autoClose?: boolean)