Those are not raw NAND chips, they are one-chip SSDs similar to eMMC, but Apple proprietary.
Apple uses several chips to set up a RAID configuration with the Mx chip as the storage array controller, presenting to the OS as a complete volume.
The Mx seems to also need to access additional data not available in storage mode to get system configuration data, like serial numbers, storage configuration, board firmware and so on to be able to boot.
Replacing the storage chips on M1 macs is possible, but requires chip taken off a working Mac and install them in the exact order as the original. From what I remember a NAND programmer is also needed to re-write serial information