Based on the documentation that aws-load-balancer-attributes is replacing the deprecated annotations, i tried this:
service.beta.kubernetes.io/aws-load-balancer-attributes: access_logs.s3.enabled=true,access_logs.s3.bucket=my-access-log-bucket,access_logs.s3.prefix=my-app
But this does not seem to work on istio loadbalancer and I see the access logging is still off:
But the same works fine while using the depcrecated annotation 
service.beta.kubernetes.io/aws-load-balancer-access-log-enabled
service.beta.kubernetes.io/aws-load-balancer-access-log-s3-bucket-name
service.beta.kubernetes.io/aws-load-balancer-access-log-s3-bucket-prefix
What am I doing wrong here?