It is impossible to implement E2EE without the information in [2] that is not present in [1]. [2] is how you get access to the storage key that Element etc used

It is impossible to implement E2EE without the information in [2] that is not present in [1]. [2] is how you get access to the storage key that Element etc used to store encrypted secrets in your account data. So if anyone's goal is to build a Matrix client that's actually useful, [2] is unavoidable.