When I talked about EM shielding I wasn’t strictly talking about shielding metal plates inside your computer. Although certain components might be shielded with metallic plates most components are tested for EM compatibility with other devices (they have to by law) and there are different possible levels of EM interference resistance and hardening. What I’ve noticed with cheap brands is that their components usually tend to be cheaply built and very susceptible to EM interferences. This doesn’t happen in brands like HP or Asus, they take a lot of attention to that detail. And yes, that typical copper heat shielding sometimes doubles as EM shielding.