Is this true ?

Program and Reprogram Your Car Remote Key Fob Control Transponder - Program Your Keys Free Instructions - Program Keys - VW Audi Seat Skoda

and if so then 1997 until when ?

Does this do door opening and immobiliser ?

That migt get the remote working again, thats a simillar process to early Ford Mondeos. The key will still not start the car, you do need a laptop or dealer to do that.

I thought it seemed a little too easy.

The instruction on the page above is only for re-synchronizing already matched remotes. It does not program keys and especially doesn't do anything immobilizer related.