Extract multiple bands from a raster layer with wps ras:BandSelect

I’m trying to use the WPS process ras:BandSelect tool to select multiple bands from a 10-band raster layer. Specifically, I want to select band indices "0, 1, 2" from the 10-band image.

The DescribeProcess abstract for ras:BandSelect is "Returns a raster generated by the selection of some bands from the input raster" which suggests selecting multiple bands is possible.

Below is the XML payload that I’m posting to the WPS service. However, this payload ONLY returns band index "0" and not the three bands I’m interested in.

Is selecting multiple bands possible and if so, what synatax can I try next?

Note, WPS server is Geosever 2.15.

<?xml version="1.0" encoding="UTF-8"?><wps:Execute version="1.0.0" service="WPS" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.opengis.net/wps/1.0.0" xmlns:wfs="http://www.opengis.net/wfs" xmlns:wps="http://www.opengis.net/wps/1.0.0" xmlns:ows="http://www.opengis.net/ows/1.1" xmlns:gml="http://www.opengis.net/gml" xmlns:ogc="http://www.opengis.net/ogc" xmlns:wcs="http://www.opengis.net/wcs/1.1.1" xmlns:xlink="http://www.w3.org/1999/xlink" xsi:schemaLocation="http://www.opengis.net/wps/1.0.0 http://schemas.opengis.net/wps/1.0.0/wpsAll.xsd">
      <ows:Identifier>ras:BandSelect</ows:Identifier>
      <wps:DataInputs>
        <wps:Input>
          <ows:Identifier>coverage</ows:Identifier>
          <wps:Reference mimeType="image/tiff" xlink:href="http://geoserver/wcs" method="POST">
            <wps:Body>
              <wcs:GetCoverage service="WCS" version="1.1.1">
                <ows:Identifier>the_layer</ows:Identifier>
                <wcs:DomainSubset>
                  <ows:BoundingBox crs="http://www.opengis.net/gml/srs/epsg.xml#27700">
                    <ows:LowerCorner>bbox_ll</ows:LowerCorner>
                    <ows:UpperCorner>bbox_ur</ows:UpperCorner>
                  </ows:BoundingBox>
                </wcs:DomainSubset>
                <wcs:Output format="image/tiff"/>
              </wcs:GetCoverage>
            </wps:Body>
          </wps:Reference>
        </wps:Input>
        <wps:Input>
          <ows:Identifier>SampleDimensions</ows:Identifier>
          <wps:Data>
            <wps:LiteralData>0 1 2</wps:LiteralData>
          </wps:Data>
        </wps:Input>
        <wps:Input>
          <ows:Identifier>VisibleSampleDimension</ows:Identifier>
          <wps:Data>
            <wps:LiteralData>0 1 2</wps:LiteralData>
          </wps:Data>
        </wps:Input>
      </wps:DataInputs>
      <wps:ResponseForm>
        <wps:RawDataOutput mimeType="image/tiff">
          <ows:Identifier>result</ows:Identifier>
        </wps:RawDataOutput>
      </wps:ResponseForm>
    </wps:Execute>

    <wps:Input>
      <ows:Identifier>SampleDimensions</ows:Identifier>
      <wps:Data>
        <wps:LiteralData>2</wps:LiteralData>
      </wps:Data>
    </wps:Input>
    <wps:Input>
      <ows:Identifier>SampleDimensions</ows:Identifier>
      <wps:Data>
        <wps:LiteralData>1</wps:LiteralData>
      </wps:Data>
    </wps:Input>
    <wps:Input>
      <ows:Identifier>SampleDimensions</ows:Identifier>
      <wps:Data>
        <wps:LiteralData>0</wps:LiteralData>
      </wps:Data>
    </wps:Input>    
    <wps:Input> 
      <ows:Identifier>VisibleSampleDimension</ows:Identifier>
      <wps:Data>
        <wps:LiteralData>0</wps:LiteralData>
      </wps:Data>
    </wps:Input>