So put a few simple plastic boxes in the boot if you need organised storage. A few elastic straps will keep them in place. A little tiny net on one side of the boot won't help a lot.
Yes, I agree it is bad that SEAT publish the exact details of what is included and then change it - but that is why they always publish a disclaimer that things may change.
Already got a boot tidy! When I started this thread, it wasn't known that SEAT had deleted the net. If the dealer comes back with a 'no' regarding the parts, then fair enough. I've got better things to do than argue about such things.
All the best
Andy