Lane assist is camera based.
I was thinking that highbeam assist would operate on the same sensor that the auto lights operate on (which is on the inside of the windscreen at the base of the rear view mirror stalk attachment) if no further hardware is required. If further hardware is required then perhaps it is an enhanced light sensor, or additional one somewhere.
As with the XDS on the Scirocco - VW aren't shy on charging you for an option that requires only VCDS activation.