That could be related to anaconda installer (or kickstart scripts) peculiarities when reusing a disk:
If you selected automatic partitioning and I would like to make additional space available , or if there is not enough free space on your selected hard drives to install CentOS, the Reclaim Disk Space dialog box opens when you click Done , and lists all configured disk devices and all partitions on those devices.
To reclaim space, select a disk or partition, and click either the Delete button to delete that partition, or all partitions on a selected disk. (…) If you delete a partition, all data on that partition is lost.
Alternatively, you can click Delete all , this deletes all existing partitions on all disks and makes this space available to CentOS. Existing data on all disks is lost.
Click Reclaim space to apply the changes and return to The Installation Summary window.
No disk changes are made until you click Begin Installation on the Installation Summary window. The Reclaim Space dialog only marks partitions for resizing or deletion; no action is performed.