Counterfeit mainly just means it's pretending to be something that it isn't. It's entirely possible this drive has the advertised capacity (though I wouldn't count on it), but it would still be a fake.
Specifically, that each buried gate can store one bit (SLC), two bits (MLC), three bits (TLC) or even more.
Obviously more bits means closer thresholds, making the gate more susceptible to electrical noise when reading and writing (and process variation in the dopant loading).
It's pretty easy to think up ways to pack in more bits that would slow down the read rate... such as applying multi-level ECC or just waiting longer for the read ADCs to settle.
For context, actual "real" low-end NVMe drives are 2TB for ~$180. The Samsung is $300 for 2TB right now. I could easily see you cutting cost by using used NAND and horrible controllers and get a cost much lower.