I was referring to them saving encrypted data on their servers. Isn't that e2e encrypted? If not, does that mean an adversary with access to their database knows my chats?
That is not end-to-end encrypted, no. The company has all the information necessary to retrieve your plaintext conversation data. They can (and likely do) encrypt this data at rest within their infrastructure, and they can make it as hard as they want for an individual employee to access this information, but fundamentally you're trusting that their internal controls are sufficient.