In the current doc we say that using VDDK will accelerate migration.

Current Statement :
"
The Migration Toolkit for Virtualization (MTV) can use the VMware Virtual Disk Development Kit (VDDK) SDK to accelerate transferring virtual disks from VMware vSphere.

Note
Creating a VDDK image, although optional, is highly recommended.
"

We need to communicate that using MTV without VDDK is not recommended.
Something along the lines of

"The Migration Toolkit for Virtualization (MTV) SHOULD be used with the VMware Virtual Disk Development Kit (VDDK) SDK for transferring virtual disks from VMware vSphere.

Note:
Using MTV without VDDK is unrecommended and may result in significantly lower migration speeds.