Methinks it is not a "feature," but a "bug." My 99.5 (US) Jetta (I know, but I doubt VW did anything different between the two models even across the N.A. market) didn't do that. The "opposite" is a feature -- if you hit the trunk/hatch release, even if you get out of the ca, but don't release the second catch for the trunk/hatch pretty quickly, it will lock itself again.
Your friend might have the dealer (or someone with a VAGCOM unit, though I'm not sure the VAGCOM can read alarm module error codes) check out the alarm module (warning: it's not a cheap fix -- he may choose to live with it).
sd