These are clearly knockoff parts because they are being marketed as Apple brand bumpers= goes against OEM contracts
the bumper could be made by Microsoft, but if it's the official apple bumper then it's OEM
it's clear that you don't understand what the term OEM stands for so I'll give you a real life example
2002 Honda Accord Gauge cluster
Manufactured by Ford
in every new Honda Accord, Ford is the "original equipment manufacturer" for this Honda part
Ford could sell the gauge cluster as a ford part (if it signed a non-exclusive contract, hell it could sell the part to Toyota ), but it cannot sell it as a Honda part.
there is only one OEM bumper that is the one apple sells , the rest are replica's,knockoffs, or "oem style"