Fwiw, SATA and NVMe are mutually incompatible concepts for a single device; SATA drives use AHCI to wrap ATA commands in a SCSI-shaped queuing mechanism called command lists over the SATA bus, while NVMe (M.2/U.2/add-in) drives talk NVMe protocol (multiple queues) over PCIe.
For a drive, yes, SATA and NVMe are mutually exclusive. The M.2 slot can provide both options. But if you have a machine with a M.2 slot that's only wired for SATA but not PCIe, your choices for drives to put in that slot have been quite limited for a long time.
At least the Samsung and SanDisk PCIe AHCI M.2 drives were only for PC OEMs and were not officially sold as retail products. There were gray-market resellers, but overall it was a niche and short-lived format. Especially because any system that shipped with a PCIe M.2 slot could gain NVMe capability if the OEM deigned to release an appropriate UEFI firmware update.
