It does.
On the 'rents Audi, if you press the boot button, the boot pops. However the
Ibiza doesn't have this mechanism built into the boot lock. But now with the 3 button key, if you walk up to it (locked car) and press the boot button, just the boot unlocks. Close the boot, and it re-locks automatically. The whole time, all the doors remain locked.
Have you given it a go with VAG-COM/VCDS? If so, remember you need to re-code all the remotes (old and new) for the car at the same time.
The other option (assuming you are
coding it correctly) is that the remote part of the key is knackered. Believe me it does happen, my dad's VW T5 van had hundreds spent on it trying to make the remotes work, 2x new CCUs, new wiring to the CCU etc when the real
problem was actually that the remotes of BOTH keys were just knackered!
You could always buy just the remote bit off eBay for £20 (new), pop your bladed part on, code it and see if it works?