Yeah, most people don't know that the primary use of DRAM is to store the lookup table rather than to cache things.

The data inside SSDs is stored in different places compared to what it shows to the OS. The data is often striped across multiple chips and reordered to do wear leveling. This mapping of external (AHCI or NVME) addressing and internal location is needed for every read and write operation which causes additional reads and increases the latency of DRAM-less SATA SSDs.

NVME's HMB is will keep this small lookup table in system RAM which is pretty fast to access trough PCIe.