It's an interesting question!
I think that the instances are terminated when they are spun down therefor the behavior should be the same as if you terminated them yourself manually

Okay, I'm going to look into this further. We had around 70 volumes that were not deleted but could have been due to something else.

Hi RobustRat47 , the volumes should auto deleted

Yep figured this out yesterday. I had been tagging G type instances with an alarm as a fail safe if the AWS autoscaler failed. The alarm only stopped the instance and didn't terminate it (which deletes the drive). Thanks anyway CostlyOstrich36 and TimelyPenguin76 🙂