Zero-knowledge vs encrypted at rest
Both phrases appear on security pages. Only one of them means the provider cannot read your data.
The provider holds the key.
"Encrypted at rest" means data is encrypted on the provider's disks. It is worth having — it defends against stolen drives and some classes of breach. But the provider holds the key, which means the provider can decrypt. So can anyone who compels or compromises them.
The key never reaches the provider.
Zero-knowledge means encryption happens before transmission, with a key the service never receives. The provider stores bytes it cannot interpret. The distinction is not one of degree — it changes who is capable of reading your data, not merely who is permitted to.
Ask what happens when you forget the password.
It is the fastest test there is. If a service can restore your access after you forget your password, it can read your data — those are the same capability described two ways. If it cannot, it is telling you something real about where the key lives.
SEES cannot. That is not a missing feature; it is the property being claimed.