In Subset you have a Source and a Target Schema. They relate to the Database Source and Target user but are not the same.
The users might have access to several schemas.
Using Source User SRC1 you may have imported tables from Schema SRC1 and SRC2.
Using the Target user TGT1 you like to subset the data to two schemas. Because Subset is smart but not clairvoyant you are priovided with a list of schemas the user TGT1 has permissions for.
But: Is it correct that Subset for Oracle does not show all Schemas as targetschema?
Yes you are correct
We obtain this data using the following query:
select distinct table_schema from all_tab_privs union all select user from dual
And from this liste we filter out the following schemas: