As far as I can tell the link is just for the key-less remote control, not immobiliser chip.
Learnt how to use VAGCOM and the cable today.
Bought a new fob carcass and a second hand fob including the guts.
There are three parts. The key blade, the immobiliser chip and the circuity that does the unlock/lock/boot.
Using the new fob carcass, the second hand fob and my duff one I made a working one and then coded it to the car with the VAGCOM. Quite proud of myself
Just a word of warning - I think the link above to the rosstech site is missing a step.
You can't add a new fob to an existing setup.
You need to delete all fobs from the car and then add them all together.
Like this -