Although optimized hosted feature layers were added as an option to AGOL this year, the documentation has the following caveat:
"The basemap on which the feature layer is drawn must use the Web Mercator Auxiliary Sphere projection (such as Esri default basemaps) to see improved drawing times. When the layer is added to basemaps with projections other than Web Mercator Auxiliary Sphere, the layer is loaded without optimization."
This means organizations that have standardized on other projections cannot take advantage of this feature.
Please make this feature compatible with all projections.