No, you miss the point here. Now I'm not saying this in a "God how thick are you?" way so please don't interpret as such. However this digs into the real fundamentals.
What is the definition of an opportunity? Things like a possibility, a prospect, a good position. Any thesaurus will come up with synonyms like chance, shot, prospect etc.
Aguero was denied the opportunity to get into an obvious goal scoring position by unfair means. Had he not been pulled he would have got there. Now had the ball not been crossed then indeed, it's a penalty and maybe a caution.
Let's take another example of a DOGSO when the fouled player is not in possession of the ball. You (the reader) is the attacker, and I'm the centre half, and I've had the beating of you all day (It's my story so I can!). You've been trying to play on my shoulder as last defender but I keep timing my offside perfectly. We're in or around the 'D'. Your teammate sends another through-ball into the penalty area I step up to catch you offside but immediately realise you've done me. I turn and grab a massive handful of your shirt before you can reach the ball. You haven't touched the ball because I've stopped you, but I still know I'm off. (unless lightning strikes twice - I did this for real once and the striker punched me. He got a red, I got away with it!) I've denied you that obvious opportunity even though you did not have the ball because the likelihood was you would play the ball before me or my goalkeeper .
There were some interesting DOGSO videos on either the FIFA or UEFA sites, and at least one showed something similar.