> After this second secret key was also cracked it was discovered that the key is common to all FM11RF08 cards, as well as other models from the same vendor (FM11RF32, FM1208-10), and even some old cards from NXP Semiconductors and Infineon Technologies.

Even the ones not made by a Chinese company had the same backdoor. Perhaps, the original design had this backdoor and the manufacturers simply implemented the design. NXP is Dutch. Infineon is German.