Poor choice of words "Power off the machine". Suggestion: have options for "Graceful Shutdown" instead of this option to "Unplug Power".
Bring it in line with other OSes. For instance Windows does not have such a drastic option. The Power Off button is a Graceful Shutdown operation.
Power off the machine: With this option, Oracle VM VirtualBox also stops running the virtual machine, but without saving its state.
Warning
This is equivalent to pulling the power plug on a real computer without shutting it down properly. If you start the machine again after powering it off, your OS will have to reboot completely and may begin a lengthy check of its virtual system disks. As a result, this should not normally be done, since it can potentially cause data loss or an inconsistent state of the guest system on disk.
As an exception, if your virtual machine has any snapshots, see Section 1.11, “Snapshots”, you can use this option to quickly restore the current snapshot of the virtual machine. In that case, powering off the machine will discard the current state and any changes made since the previous snapshot was taken will be lost.