Hi Graham
We meet again. Glad to see you over here.
I may be wrong but I believe that the answer is because the 3rd party defragger does not 'see' the snapshots and therefore will defrag based on what it sees, ie, the Windows OS view of your disk. Running the baseline, I suspect, merges the snapshot position with the new Windows OS view of the disk.
I am hypothesing here but that is what I feel is likely to be the reason. I am sure that Nick will be along to put us right on this.
Again, nice to see you over here.
