It appears that the ability to disabe editor tracking is only supported in AGOL Hosted Feature Layers and not Enterprise Feature Layers. It would be awesome to also have this functionality for Enterprise Feature layers as well. (Enhancement request #ENH-000118710 , case #02230037 ).
Please see justification below:
The user uses a federated ArcGIS Server as their hosting server. The user has set up a distributed collaboration between their Portal for ArcGIS and ArcGIS Online, and then shared their server services to ArcGIS Online as collaborated contents.
Within the latest ArcGIS Online, users should be able to select whether to "show when last edited" for their feature services on the pop up configuration according to this article: https://www.esri.com/arcgis-blog/products/arcgis-online/announcements/new-arcgis-online-functionality-supported-by-customer-ideas-december-2018.
However, this option is not available on the pop up configuration of the user's collaborated contents (server services) even though the user had enabled editor tracking when they published the feature layer. It turns out this functionality is only available for hosted feature layers, because "show when last edited" option is considered one of the editing settings, and users cannot enable or modify editing settings for server services from ArcGIS Online.
