Oracle Database enforces a
PRIMARY KEYintegrity constraint on a table by creating a unique index on the unique key or primary key. This index is automatically created by the database when the constraint is enabled.
For user named PK/UK constraint we cannot distinguish if support index is created by database or there is an index explicitly created by the user.
There are customers having explicitly created indexes in their model having the same name as PK/UK constraint. Discarding such indexes during import will discard valuable information about storage properties related to PK/UK constraint.
Support indexes for database named PK/UK constraints are discarded during import.
BTW you are labeling your posts with 4.0 EA1 but in fact that's SQL Dev 4.0 EA1. DM 4.0 EA1 was released Today and you can check that version for your problems.