Hello @Matthew Blessing
The reason these disks show up in the Advisor Cost Recommendations is because they are still considered as active disks and are consuming storage resources however aren't yet attached to any VM. ASR just replicates managed disks without a VM, only upon a failover/Migration it creates the VMs using those replicated disks.
So, Azure Advisor sees them as just unattached disks in the subscription and reports them based on cost cutting recommendations as per the below advisory.
Evaluating such recommendations is must as suggested in the above document link.
Hope this helps!
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