I have an application developed using on on-premise portal which we planned to also deploy using agol (making the bold assumption that feature layers would be defined the same).
Now that we have moved to agol I find that agol feature services do not have subtype definition. I have published the same service to portal and to agol. In portal if I look at the json I see the subtype definition, but this does not exist in the agol layer definition. How can this be? How could there possibly be a core new feature of the 100.3 API and not have it supported when using an agol layer. So all this nice clean logic based on subtypes developed for a featurelayers created in ArcGIS Enterprise cannot be used in the application when it uses agol layers and instead have to go backwards and use logic based on FeatureTypes (which was removed from the application in favor of the subtype logic). All I can do is shake my head as I work late into the night trying to fix the application to work with agol.