uses
Heights are orthometric (gravity-related/MSL), so an ellipsoid-datum consumer must add the geoid undulation. Sources in declaration-strength order: heightModelInfo.heightModel, the vertical CRS wkid, an embedded VERTCS/VERTCRS in spatialReference.wkt, then the vertCRS name. Nothing declared means ellipsoidal (HAE), matching how a package without a vertical CRS reads. The undulation applied downstream is always EGM96, so an EGM2008/NAVD88 package lands within the sub-metre difference between those geoids.