It seem to be inconsistent to me that all groupBy endpoints except the ratio/groupBy/boundary are structured like this:

{
groupByResult:[ 
                   result:[ ... ],
                   groupByObject
]
}

only the ratio/groupBy/boundary uses 'groupByBoundaryResult' instead of 'groupByResult' like this:

{
groupByBoundaryResult:[ 
                   ratioResult:[ ... ],
                   groupByObject
]
}

The "normal" /groupBy/boundary does not use the groupByBoundaryResult but the common groupByResult as all the others.

To me there seems no need for different naming of the groupByResult.