Hi Leo,
When you create a new feature class in Oracle it is listed by "OwnerName.Table Name" (i.e. George.FeatureClass)
The GIS user is not the "admin" account for Oracle. By default the SDE user is the geodatabase administrator (who owns the geodatabase (SDE/GDB) repository tables).
As for loading the data as the GIS user, that is up to you. I would say that it make administration of the data easier to have a separate data owner.
Here is some documentation on Oracle and owning data:
User Accounts in Oracle
GDB Admin in Oracle
What are user privileges
User privileges for Oracle
If you need more detail or help, I would recommend opening a Esri Support ticket and talking to the Geodata team.
-George
Geodatabase Enterprise GIS
--- George T.