As per BSA user guide.
Enables creation of WinPE images. Required for provisioning Windows preboot environments; otherwise, not needed. Typically installed on the same host as the PXE server.
Use version 2.1 for all operating systems except for Windows 2008 R2, which requires AIK version 3.x.
So apparently for 8.6Sp1 ( potentialy earlier versions ) if you want to use WIM provisioning you must use a WinPE4 or WinPE5 based image. For some reason this change was made without also updating the 'Provisioning Image Creation' process in 8.6SP1 to enable using the new WinPE4/WinPE5 toolkit for creating images. Instead, there is a 'workaround' detailed at:
This involves replacing the base image for the WAIK from the packaged WinPE3 image to one provided by BMC support.