I have a hunch unless EBC can get the backing plates from Europe, they are likely using NRS plates. NRS is one of the major aftermarket suppliers of brake backing plates and shims. Japanese and Korean calipers are known for pad clunk if the pads don’t fit as precise as the OEM(Advics, Akebono, NBK, Hitachi, Nissin, Sangsin or Mando). Hence why there’s better experiences with them on European and “American” cars with ATE or TRW calipers.
I’ve had Wagner, Centric, PBR and Bendix clunk. None with OEM or Akebono.