I don't think that's an interpretation at all. Blizz has stated (blue post linked earlier) that they consider one "keystroke" to include both up and down.

Blizz does have a number of things they allow to all be on the same keystroke (e.g. a WoW macro doing /assist <char>; /cast Fireball) and that's obviously perfectly fine. I'm sure if I took those 2 actions and split them into a keydown/keyup via some external method Blizz wouldn't really care, if they even noticed at all.

But what was suggested above is using an external tool to put 2 different /cast spells onto keydown/keyup in order to somehow get both spells to happen at the same time in order to increase your dps beyond what should be possible. That seems clearly across the line.