To iterate a bit more on this.. the whole point of RFID is that unlike a metal key where you make copies and distribute copies, thus immediately losing control of security that way, the point of RFID is / was that each key was unique and the doors or access or whatever maintained a list of allowed IDs. That way a card is lost, remove from list.. not take everyone’s cards back and program a new shared ID across all the cards.
The concept of a “magic” RFID transponder goes against this very premise and immediately breaks the idea of maintaining authorized lists vs trying to control the inevitable - lost or stolen credentials. China is the only country willing to make magic chips because it pisses off everyone in the RFID supply chain from intellectual property holders to system managers trying to control the chaos. You may find that if pressed, you won’t actually be able to find out who really manufactures these magic chips because they don’t want to be found.
In short, magic chips are grey market borderline illegal products.