ArcGIS JS WMTS SpatialReference

[Wade]

My current spatial reference assumption for the other layers is 3857. If I join WMTS later it will be 4326. Is it possible to convert 4326 to 3857?

const TOPO01K_P1 = new WMTSLayer({
            // 3857
        });

const TOPO01K_P2 = new WMTSLayer({
            // 4326
        });

TOPO01K_P2.load().then(function () {
     TOPO01K_P2.sublayers.forEach(function (sublayer) {
                sublayer.fullExtent = webMercatorUtils.geographicToWebMercator(sublayer.fullExtent);
     });
});