Why does Nova use arrays instead of objects for the props field?

In a normal Vue component, props are defined as follows:

Vue.component('user-card', {
  props: ['firstName', 'lastName'],
  template: '<p>Hi {{ firstName }} {{ lastName }}</p>'
})

However in Nova, I can't add manual props because it's defined this way:

props: [
        'card',
      'type': {
			type:String <=== This doesn't work
		}
        // The following props are only available on resource detail cards...
        // 'resource',
        // 'resourceId',
        // 'resourceName',
    ],

Why is this? And how to get around it?