Smart Action does not receive records from Smart View

[lesley-hays]

I'm triggering a Smart Action on a Smart View with a button, as per the docs. But the records don't appear to be sent to the action route.

Button looks like
<button {{action 'triggerSmartAction' collection 'Do The Action' records}}> Do It </button>

Expected behavior

Logging req.body.data in the Smart Action route should show me the record IDs used in the Smart View.

Actual behavior

Returns a mostly empty object: { attributes: { ids: [], values: {}, collection_name: 'images' }, type: 'custom-action-requests' }