arrayCoordinateSystem isn't very clear

[will-moore]

In the page at https://ngff-spec-preview.readthedocs.io/en/latest/#array-coordinate-systems I'm not clear where exactly the arrayCoordinateSystem object is stored. This sentence:

The name and axes names MAY be customized by including a arrayCoordinateSystem field in the user-defined attributes of the array whose value is a coordinate system object

Does that mean that image.zarr/0/zarr.json contains the arrayCoordinateSystem like this:

{
    "zarr_format": 3,
    "node_type": "array",
    "shape": [4, 3, 5],
    "attributes": {
        "ome": {
            "version": "0.6dev2",
            "arrayCoordinateSystem": {}
        }
    }
    //...
}

How would this change the behaviour of viewers or other tools? Would they be expected to check for the presence of this when opening the image?