Using the word dissection literally refers to a surgical dissection, as you say - but in a dissection a surgeon cuts up the thing being dissected and picks it apart. During a dissection, a surgeon doesn't "manage" what is happening carefully.

So when someone says that a QB dissected a defense, they're talking about the QB picking the defense apart with surgical precision on their passes. Wilson did that a few times last year. Romney - while good, I wouldn't call what he did dissecting a defense.