What is the plastic barrier surrounding this choke for?
Ideally it is very thin CRGOS transformer steel insulated with more plastic.  This is designed to absorb differential current noise radiate to near by magnetics and outside the box.  e.g.the  yellow taped choke which appears to be an additional CM choke to the silver common mode choke. This provides better noise reduction for RF from the SMPS and also added to improve lightning strike immunity.
The common mode coupling to nearby and radiated emissions is a common  problem and this appears to be an added differential choke for ingress/egress.