[Developer Preview] RocksDB Storage for DB and Key Value APIs ,what's the issue detail ?

https://developers.eos.io/manuals/eos/v2.1/release-notes/v2.1.0-rc1/#developer-preview-rocksdb-storage-for-db-and-key-value-apis-9340-9529

Does anyone can tell me why this feature is not yet ready for production usage？ Anyone can tell me the details, please? I need to explain to my client for the details.

Thanks!