Just to be clear, does it say anywhere that Slack does/doesn't retain access to the key store? It seems like it would be impossible for the service to work with

Just to be clear, does it say anywhere that Slack does/doesn't retain access to the key store? It seems like it would be impossible for the service to work without maintaining access to the keys from their servers, so nobody should expect this to provide end-to-end privacy. Is that correct?