Hi DennisBSE,
It is not true what you were saying, CBT should be working and it's fully supported by DP7.01, in fact, there is a 7.03 patch bundle on the streets allready.
In my envoronment it works flawlessly, CBT enabled took only used space, doesn't matter if my VMs has thin, thick or whatever kind of vdisk.
Let me know if you have any questions I could help
Regards