A cursory X-Ray would show the internal SD. This product needs a hardware re-design (which I've seen other projects do) to have onboard flash instead.

Saying that, any proper investigation would read the firmware from the flash and identify the decryption routing anyway

It has an SD card because proper flash is expensive. Surely the people making "4TB" flash drives on Temu must be using the same methods, or else they will be soon.