Bug report: ElastiCache modify-replication-group affects all groups in a region, not just the specified group

I have multiple ElastiCache (Redis) replication groups in a region, and I'm trying to selectively turn off SNS notifications for some, but not all of these. However I've found that whenever I either disable or enable notifications for a single replication group, the change affects every replication group in the region, not just the one I specified.

I've been able to reproduce this on the AWS CLI and in the JavaScript SDK, here's how it looks on the CLI.

First I'm checking the existing notification configuration. I'm using describe-cache-clusters because the notification configuration is not provided by describe-replication-groups.

aws elasticache --region us-east-1 describe-cache-clusters --cache-cluster-id group1-001
aws elasticache --region us-east-1 describe-cache-clusters --cache-cluster-id group2-001

For both replication groups, the notification status looks like this:

||+---------------------------------------------------------------+-----------------------------------------------+||
|||                                           NotificationConfiguration                                           |||
||+----------------------+----------------------------------------------------------------------------------------+||
|||  TopicArn            |  arn:aws:sns:us-east-1:xxxxxxxxxxxx:ElastiCacheEvent                                   |||
|||  TopicStatus         |  active                                                                                |||
||+----------------------+----------------------------------------------------------------------------------------+||

Next I'm disabling notifications on just one of the groups

aws elasticache --region us-east-1 modify-replication-group --replication-group-id group1 --notification-topic-status inactive

At this point I would expect group1 to be inactive and group2 to remain active, as I haven't touched group2. However they have both changed to inactive:

||+------------------------------------------------------------+---------------------------------------------+||
|||                                         NotificationConfiguration                                        |||
||+---------------------+------------------------------------------------------------------------------------+||
|||  TopicArn           |  arn:aws:sns:us-east-1:xxxxxxxxxxxx:ElastiCacheEvent                               |||
|||  TopicStatus        |  inactive                                                                          |||
||+---------------------+------------------------------------------------------------------------------------+||

And it's not just group2, every replication group in the region now has notifications disabled. The same happens when I reactivate notifications on a single replication group, every replication group in the region becomes active.