Placement Rules' clusterSelector.matchExpression Not Resolving As Expected

Issue

When using PlacementRules on my ACM cluster and selecting clusters based on matchExpression key/value pairs my applications are placed on clusters that are incorrect.

For example given two clusters, one on Cloud=Amazon with Vendor=Openshift and another on Cloud=IBM with Vendor=Openshift, the following clusterSelector results in the application being placed on both clusters instead of just the Cloud=Amazon cluster.

clusterSelector:
    matchExpressions:
    - key: vendor
      operator: In
      values:
      - OpenShift
    - key: Cloud
      operator: NotIn
      values:
      - IBM