I expect that for general development use, FreeBSD in a VM performs better with UFS than it does with ZFS, especially in low memory VMs. That is probably why t

I expect that for general development use, FreeBSD in a VM performs better with UFS than it does with ZFS, especially in low memory VMs. That is probably why the vagrant images don't use it by default. You might need to just create a FreeBSD VM from the normal FreeBSD installer if you wish to experiment with ZFS on FreeBSD.