A part of this depends what you think "fiction" and "the system" are. For me, for example, the battlemap showing how things are laid out is a part of the fiction. And again I'm going to mention 4e here and how, thanks to how common forced movement is, it makes other versions of D&D feel like acting against a green screen rather than on location because you actively throw people into/onto/over/off the stuff.
I'm a big fan of 4e D&D, and I think combat in 4e feels pretty dynamic.
But some of the issues that
@FrogReaver mentions - where the cyclical/stop-motion approach to resolution means that resolution is not truly simultaneous - can come up. The greater number of off-turn actions in 4e reduces this a bit, but it's still there.
Just to given an example: suppose the PCs are defending a tower against an assault from a flying dragon, which is approaching from beneath the battlements. The fighter wants to leap onto the back of the dragon. In 4e, how that resolution is to be handled depends on whether the dragon ends its turn adjacent to the battlements, which means the fighter's player can use a move action to have their PC leap onto the dragon's back; or if instead the dragon moves past the battlements to end its turn some distance away, in which case the player of the fighter has to establish some sort of off-turn ability to perform the leap (eg via a readied action, which in 4e is a standard action).
That's a difference of technical and tactical decision-making, which can significantly affect the outcome. But what does it correspond to in the fiction? Nothing at all.
Contrast, say, Dungeon World, where leaping onto the back of the dragon would (most naturally, I think) be resolved as Defy Danger, and that doesn't depend in any sense on a turn order or technical movement rules. Or contrast Burning Wheel (Revised, not Gold - I'm not across the changes that Gold made to combat positioning), where the dragon's attempt to flyby and breathe would be an attempt to Maintain while the fighter is attempting to Close to the Inside. This is a contested check on Speed (or perhaps Speed vs Power if we adjudicate the fighter's move as a Tackle), and again we don't get the strangeness that FrogReaver is pointing to.
Certainly simultaneous action is not a narrative that follows naturally from the events that occur in D&D combat, because D&D combat is turn-based, not simultaneous. Of course, the turn-based structure of D&D combat is an abstraction, used to allow for simple, orderly action resolution, but meant to represent simultaneous action. And it is entirely possible to derive a narrative of simultaneous action from the events that occur in D&D combat, it just has to be done post-hoc.
Right. Which is the whole point - the tactical decision-making takes place primarily within a purely rules-bound space, with the shared fiction being an output of, but not an input into, that decision-making.
Another consequence, which
@FrogReaver might also have in mind, is not about the decision-making process but about outcomes. My experience of this is mostly from Rolemaster. RM has about a billion variant initiative systems in print, and in our game we used one of my devising that grafted aspects of 2nd ed and RMC onto aspects of RMSS. Within a round, resolution was largely simultaneous which avoided a lot of stop-motion issues. But round boundaries were still a thing, and occasionally an outcome would reflect not anything that made sense in the fiction, but there mere fact that a round boundary had been hit (so eg moving 50%, new round, moving 50%, attacking) might produce a different outcome from (moving 100%, new round, attacking) because of how attack/parry splits get redeclared at the beginning of each round, although in the fiction it's not really clear why it should.
It's probably true that all wargame-style, structured resolution systems can produce some oddities vis-a-vis the fiction, but I think hard round boundaries, and modern D&D's turn-by-turn resolution, can contribute to them.