I've been screwed by a counterfeit SD card and it seems like the "manufacturer" probably took older, smaller capacity cards where the back stock had outlived demand for those specs and just reprogrammed them to identify as a higher capacity, premium SD from Samsung, reprinted the label (very well), got their packaging basically identical to Samsung's, sent them to Amazon where Amazon seemingly decided they should be co-mingled with the Samsung-supplied cards and sold off as such.

For the consumer, I only realized something was wrong when I filled the actual size of the SD card and started getting errors, but still those errors came from my phone and basically said the SD want being detected and to reformat. So it could have been a phone issue. Only after going down the internet's Amazon counterfeit rabbit hole and then finding a program that checks counterfeit cards did I find out the card was actually a 32GB card with probably some awful I/O rates and not the 128GB that it was a announcing to devices. And for all that time, energy, frustration, money, and data lost to phone reformats, Amazon didn't give two craps. They said I was outside the return window and if my item was defective I should contact the manufacturer. They probably only didn't say "seller" because they were the seller, no 3rd party. It clearly want on the CS script to consider that you can't call the legitimate manufacturer about a defective counterfeit product sold as legitimate by the same business they count on to sell their legitimate products.

It could also be slower read and write speeds. Also, I'm not sure of the exact numbers, but the difference in expected life of the product could be in years, such as 1 year for a counterfeit versus 10 years for a brand name.