There is even NVMe passthrough support via io_uring, so it's still possible to send custom NVMe commands when using io_uring instead of a userspace driver: https://www.usenix.org/system/files/fast24-joshi.pdf

Normal block I/O use cases don't really need NVMe io_uring passthrough, but it addresses the more exotic cases and is available in mainline Linux. And NVMe passthrough might eke out a little more performance.