EB,
I don't think Cov is trying to deliberately goad you. I do not think he is trying to say that you are being manipulative in a way that undermines the rules in a malicious fashion. I think what he is trying to get across is that there is a certain assumption based on the principle of the feat that is being accidentally avoided based on your rules interpretation. The feat is called DUAL Implement spellcaster. The basic nature, or principle of this feat is that you are wielding two separate implements, and that you are able to use both AT THE SAME TIME to achieve a greater effect on a single spell.
Imagine these two scenarios:
1) A sorcerer is on a battlefield (and has DIS) wielding two wands. He points both wands at his enemy and recites the words that bring forth his power. The sorcerer channels the arcane energy within him into both wands at once and unleashes a powerful spell. This works exactly as the feat was written, and makes sense as such.
2) A wizard is on a battlefield (and has DIS) and is wielding a staff in two hands (he has the feat that allows the staff to be a double weapon [can't remember the name]). He channels the arcane energy within him into his staff and points it at his enemy, unleashing his spell...
Now... even giving that the staff is considered a double-weapon, and even giving that the caster is ABLE to use two implements at once, how is he going to point BOTH ends of the staff at his enemy AT THE SAME TIME? This, in my opinion, is why a staff (or any other double weapon) could not and should not be used in conjunction with DIS. It makes no sense. Once the spell is released from the implement, it has already come out of one end or the other. By the time you turned the staff around to use the other end, the attack was already made.