If it's not one still, then there are panel transitions. And that's what we're discussing, right? >_>a
Comics rarely have action-to-action panels. Mostly, they have stills of battles
Each panel is a still of something, but the space between panels is a transition. A transition can be of several classifications, the most popular in everything, being a action-to-action transition.
I'm using Scott McCloud's comic terminology for the record, as there isn't actually much else of a standard in the comic industry.
You have to think during exposition, but comic or manga, you don't think during action scenes, I believe we both understand this.
Now for me, if panel transitions in action scenes miss a small detail like a character shifting their stance or position, it really doesn't contribute much to me being confused. Frantic is frantic, we all miss little details when things move fast, I don't let it bother me.
If you leave out an important detail though, then yeah maybe one could get confused, like "where in the world did he get that BFG?" (Unless it's hammerspace played for laughs)
I don't like it when they show me everything that happens because I get bored.