Without solid third party verification that promise isn’t worth the HTML it’s written in.

On that page though it looks like most all the features are not available with E2EE, event timeline, person detection, search you name it. So imagine few if any use it, since alternative options that can locally do all that and still have E2EE.

It depends if Amazon has any way to access to the encryption key that supposedly protects the content.

The security of pretty much everything Amazon boils down to KMS.

KMS access is based on IAM policies.

If law enforcement wants access to your KMS keys, they'll compel IAM, not KMS, to give them access. If you ask KMS about it, they'll play dumb.