In general, Object names should try to be reused where ever possible. This can help with name clashes and flexibility in finding / referencing objects by name.
The implication for UObject::Rename was that when no name was passed in, it would try to keep the Object's current name, and only change it if necessary.
Expected: The second UObject will be re-parented to the first Actor, and keep its current unique name.
Actual: The second UObject will be re-parented to the first Actor, but will be given a new name.
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-41937 in the post.