It is of course normal for any (modern) engine coolant to exceed 100C, that's why pressurised systems are used.
From previous diesel towing with a Hyundai, the coolant temperature constantly fluctuates, uphill towing increases the heat to be dissipated from the engine and transmission while light throotle downhill generates very little heat.
Currently, the UK versions of Touareg get a cooling fan upgrade to 850w IF the factory-fit towbar is ordered, although at least one owner has toured Spain this summer with a 2300kg caravan, but using an after-market towbar and only the standard 600w cooling fan - but the fan upgrade might well be standard on Australia-spec Touaregs anyway.