It's a security risk because of the way total baggage reconciliation is handled in Europe.

We know it's not a security risk because we know the circumstances. However, the question is whether the reconciliation systems can cope with the fact that the same person has two tickets and two bags and two seats, but can only physically be there once (which means head count and boarding pass tally will never reconcile! Having flown EZ a lot recently - ). And if they can't cope, then the second bag will be offloaded as a non-reconciled bag.

Now B747 has pointed out ways in which this can be handled. The question still remains whether EZ can implement them (rush, I would imagine they could, as they must mishandle bags occasionally) and whether they would want to, given they stand to make less money by allowing a passenger to do this. IME, EZ are not hugely generous in such circumstances (although I do very much appreciate the ability to change flights on the day of departure!).