ArcGIS Enterprise by default uses the ArcGIS Survey123 web API. Much like how Portal for ArcGIS can use it, or ArcGIS Online basemap services.
You can install the Survey123 website alongside a deployment of ArcGIS Enterprise. This is required to support a disconnected environment. Installing the Survey123 website requires configuration by a system administrator.
You should only do this if is required as there are no benefits, but there are disadvantages and limitations.
https://doc.arcgis.com/en/survey123/reference/survey123withenterprise.htm