buttonLabel option of electron dialog seems not working

According to the documentation (https://github.com/electron/electron/blob/master/docs/api/dialog.md) , I should be able to change the text on the confirmation button using buttonLabel option. However,

const {dialog} = require('electron').remote;
//...
dialog.showOpenDialog({
  title: '',
  buttonLabel: 'Save',
  properties: ['openDirectory', 'createDirectory']
}, (result) => {
  //...
})

The confirmation button is still shown as 'Open' instead of 'Save'

I'm in macOS 10.12.4.

Can anyone help?

Thanks.

via nt.jin