Currently, according to this FAQ, when you publish a hosted item to AGOL, you cannot Overwrite that item through the AGOL GUI or using a python script with FeatureLayerCollection.manager.overwrite(). You can only overwrite from Pro. This seems like a major oversite. We have experienced issues with older hosted items when overwriting them from Pro. We often will start in Pro with publishing and then use a python script to update that data. That is no longer a possibility.
