This is what arcgis pro arcpy gave me for the name of the sde can of the data source on and sde layer:
This is from "lyr.dataSource"
This is most definitely not the name of the sde can. "old" arcpy (for the desktop) gives me the sde can name. Can I get it the arcgispro arcpy?
I did what I should have before I posted this question - read the documentation. Looks like this is by design. Layer dataSource obscures sde can names in arcgis pro.
I was going to delete this question, but I am unable to for some reason. It will serve as a warning about not doing due diligence before you start asking questions.