shouldCancelStart unexpectedly ignored

I have a long press on my sortable component and I don't want sorting to start after the long press. I set `shouldCancelStart` to `true` but it DOES start, event though I would expect it to not start.
Simplified example for the purpose of showing the bug:
```
this.setState({isSorting: true})}
distance={3}
onSortEnd={(sort) => this.onSortEnd(sort.oldIndex, sort.newIndex)}
shouldCancelStart={() => this.shouldCancelStart}
>
{this.props.views.map((view, index) => {
return (

```

Is this wrong usage?
If so how can I prevent the sort from starting?

Start at the SortableContainer handling for shouldCancelStart and compare it with the onMouseDown and distance behavior in the simplified example. Reproduce the long-press sequence, determine why the callback is ignored, and confirm that sorting no longer starts when shouldCancelStart returns true.

Written by the indexing model from the issue text.