CodeDeploy configuration specifies HalfAtATime, but deployment history shows AllAtOnce

I'm trying to make sense of what I am seeing in the AWS CodeDeploy console.

I have a Deployment Group whose configuration specifies CodeDeployDefault.HalfAtATime (and in fact that seems to be the behavior I observe in my ASGs during deployment).

However when I look at the individual deployments in my history, they show a configuration of CodeDeployDefault.AllAtOnce.

What am I missing here?