Hello,
I think I may confirm a similar problem.
Running PD 16.0.1 on macOS Mojave here.
I've performed system updates in several macOS guests as well as in a Windows guest (such updates tend to temporarily increase the used disk space in the guest) and in all cases the disk space used on he host now remains far higher than the one reported in the guest OS.
For example:
As reported by a Windows 10 2004 guest - used: 25.9 GB, free: 37.1 GB
As reported by PD - hard disks: 35.81 GB, snapshots: 0 KB, misc: 37.1 MB, retrievable: 0 KB
VM size in the host Finder: 36.08 GB
Another example:
As reported by a macOS 10.4.6 guest - used: 17.27 GB, free: 51.18 GB
As reported by PD - hard disks: 33.4 GB, snapshots: 0 KB, misc: 1.1 MB, retrievable: 0 KB
VM size in the host Finder: 33.42 GB
Before the guest OS updates, the sizes of those VMs as created in PD 15 (or earlier) were respectively ~29 GB and ~21 GB.
I've been unable to find a way to retrieve those huge wastes...
Axel