How can an unbranded SD card be fake? Fake with respect to what?
A brand brings this value: expectations.
If I buy a no-brand item, I'm not sure what expectations I can have, and I'm not sure I can even claim that it's a fake, since I have no reference point as "the true item".
I mean that's literally the biggest value that a brand brings to you, the consumer.
That's also why brands work hard to build up and maintain good reputations.