The WD Blue SN550 utilizes a WD controller (SanDisk 20-82-01008-A1) and SanDisk 96-layer BiCS4 3D TLC NAND flash with the 60523 1T00 part number. Expreview recently purchased a WD Blue SN550 that was manufactured on July 28, 2021. The publication noted that NAND flash on the new revision carries the 002031 1T00 part number.
Besides the dissimilarity in NAND flash, the new revision also comes with a different firmware. While the original WD Blue SN550 features the 211070WD firmware, the revised unit used the 233010WD firmware. Curiously, the WD Green SN350's firmware also start with 23.
The firmware for the previous and new revisions aren't interchangeable with each other. You can't flash the 233010WD firmware on a unit with the 211070WD firmware or vice versa. In fact, the Western Digital Dashboard software doesn't even pick up the 233010WD firmware for the older units. This seemingly tells us that something has changed on a hardware level. Since Expreview confirmed that the new revision still employs the SanDisk 20-82-01008-A1 SSD controller, the NAND flash is the only other possibility.