You addressed main variations:
- Fiberglass not plastic
- STi emblems not attached
The authentic also have double sided tape already on the backside of the skirt, behind where the emblem is already attached. They also have more mounting points than the replicas, as no doubled sided tape is included by STi when you purchase authentic(aside from the preinstalled tape)
The problem is when the skirts are attempted to be passed on as authentic. That's unethical and a disgrace. Sell and Own them for what they are.
Enjoy, the replicas are a stylish bargain.