Good afternoon @ErickVereau, 
Thank you for posting. I am seeing this bug fixed, however, I think there may be a step missing in the workflow. See my video below - 
You will still see the same message - Data already belongs to a hosted layer unless you delete the layer from the TOC. 
- Add a layer from Excel
 - Share the layer to AGOL/Enterprise
 - Delete the layer from the map
 - Try to add the layer from Excel again
 
Let me know your outcome! 
Best, 
SC
					
				
			
			
				
	Shannon Cardoza
Product Engineer