I'm no expert, but intuitively it would seem that encryption-inside-encryption would be snake oil when they're meant to guard against the same layer/attack vector/threat model: for example, if you nest Serpent inside AES for a single local file encryption operation (ahem, TrueCrypt), that seems very gimmicky.

But if the encryption are supposed to protect separate and independent OSI layers or operation steps, then it would seem to me it's fully valid - specifically, in this case: - TLS dissolves inside HTTP-HTTPd endpoints or any reverse proxies, if used - additional SRP-negotiated AES dissolves inside client to the process doing key handling - final "actual" key encryption, handling at-rest encryption, and to make sure it's zero-knowledge to the storage handler

They seem to me to be guarding information leakage against very different parts of the key mangement process (storage, manipulation, http transport), and that doesn't seem to be snake oil to me.