SSD-grade is the term used for flash with a low initial defect rate. See eg. https://www.szyunze.com/wp-content/uploads/2023/08/SpecTek-N... (from https://www.szyunze.com/spectek-unveiling-truths-about-degra... )

Lower-grade flash with higher initial defect rates is what gets used in USB flash drives and SD cards, and some bargain-bin SSDs with lower usable capacities (ie. 960GB rather than 1TB).

The stuff used in a WD Black or WD Blue branded consumer SSD is not a different quality grade from the stuff used in any other mainstream consumer SSD, Apple's included.