Not necessarily fake. WD (Western Digital) owns SanDisk, so many WD Green SSDs do use SanDisk-labeled NAND chips-but not always. WD sources components based on availability and cost, so it's possible to get a genuine WD Green SSD with NAND chips from other suppliers, or unlabeled ones.
As long as you buy from a trusted seller and the packaging, serial number, and performance check out, it’s likely genuine-even without a visible SanDisk chip.