There are different ways to "turn off" obd 2 codes such as rear 02s. The tuner can just turn them off/"delete them" which WILL make you fail, but there is also a mode that tells the computer to always send an "okay" code. This mode makes OBD2 think that everything is working perfectly fine with the equipment, even if it's not. If OBD2 thinks everything is fine, then the state believes that too, ergo you pass inspection.