Think the game pass app creates a hidden partition on the end of the c drive. I just cloned my c dive to a new drive and needed to extend the main partition, the only way I could do it was to delete the ~1GB partition that was on the end. App's/Game should not be able to mess with drive partitions! The game pass app no longer works now but will not be using it anyway, just a heads up.
There's nothing on my PC using Disk Management console.