In theory it adds a speed bump. Apple as the cloud service provider can respond to the legal order by saying they don't have the key. And then the police can ask for a booby trapped update for just your phone which may or may not happen. Or they can lobby the legislature for an encryption backdoor for all devices which will force them to show their hand in terms of "lawful intercept" capability.
If you want maximum security use an air gapped computer. But that won't let you send messages on the go.
If you want maximum security use an air gapped computer. But that won't let you send messages on the go.