[formerly_proven]

A 32-byte key would allow using NVMe KV directly for content-addressed storage; many of those systems use 256-bit / 32-byte cryptographic hashes as keys. Notable exception would be git with 20-byte keys.

[londons_explore]

You can still do this... Just use the first 16 bytes as the key, and the 2nd 16 bytes as the start of the data.