Full and Incremental VMware backups are basically the same size

I've got a 5230 appliance (master/media) in a remote site with mostly VMs being backed up.  I have my VMs configured to be selected by a policy using VIP, and I have Accelerator enabled.  In my VMware policy tab BLIB is enabled (not an option with Accelerator, I think?), I'm using SAN transport with NBD as secondary transport option.

My admin console reports that incremental bacukps are *consistently* about the same size as fulls as well as full-rescans.  I'm wondering... is this considered "normal" behavior for VM backups using Accelerator?  If so... I wonder why?  If I run a client report, the incrementals show far fewer *numbers* of files backed up, but the size is about the same as a full.