Expected Behavior:

When you open a rest api page you see the fields under the group of cmb2 but this should be possible to change it based on the needs.

Actual Behavior:

Right now is not possible.

Possible Solution

Add a filter there https://github.com/CMB2/CMB2/blob/develop/includes/rest-api/CMB2_REST.php#L237