Your proposed solution is not that simple. You make it sound like EA simply used the wrong query.
> One, if EA is technically incompetent enough to allow such a severe bug to exist, they won’t have the technical skills to discern who used the promo code more than once.
The bug was not that obvious, and doesn't necessarily imply lack of technical skill. On the other hand, finding out who used a promo code more than once, as long as these things have been logged, should be trivial for any admin.
That a promo code could be used more than once, or that you could use it in ways it was never meant to? Of course the problem it's not simple, but anyone who thinks it is shouldn't be working on these things. Either someone screwed up building the system, or someone thought they could use it in ways it wasn't intended and screwed up. Sure, the solution might not be as simple as a lack of server-side validation, but either way, the solution is simple, the problem isn't.
> One, if EA is technically incompetent enough to allow such a severe bug to exist, they won’t have the technical skills to discern who used the promo code more than once.
The bug was not that obvious, and doesn't necessarily imply lack of technical skill. On the other hand, finding out who used a promo code more than once, as long as these things have been logged, should be trivial for any admin.