I'm drawing on examples from the Apocalypse World and Dungeon World rulebooks and from
actual plays (though it's been a while since I've watched any).
This doesn't mean you aren't missing the point.
Not necessarily. In the Apo World rulebook example of play, gangers show up in follow-up scene after a PC rolled a 10+ on a Move. Furthermore, the GM has the agency to not allow PCs to make a move by enforcing a Hard Move by his side. Again in the Apo World example, the GM makes a Hard Move - the PC cannot dodge the grenade. The fiction, of course, poses some restraints on the GM. At the same time, he's got a lot of ways to manipulate the way things go and what can happen and what can't happen. In trad games, there are more game world physics that constrain the action.
That's... not how hard moves work. A 'soft' move is one that sets up danger -- the ganger throws a grenade, what do you do? A 'hard' move inflicts the results of the danger, which you're only supposed to do if a roll is failed or the players ignore a set up danger. So, if a 'soft' move is to chuck a grenade into the party, the 'hard' move is it going off, either because the players ignored it or failed a check to deal with it. 'Hard' moves don't remove player moves, they result from a failed player move or the players ignoring the danger -- they flow from the established fiction. When you make a hard move it should always be from something you've already set up, and it should fit the play themes.
The follow-up scene is a new scene -- it starts the loop of 'put players into a situation' again, so having gangers show up at the start of the scene is the usual frame a problem to be dealt with.
I'm feeling pretty strongly that you've skimmed the rules but don't understand them because you're approaching it from a trad game point of view where the GM has a planned scenario and the players interact with it. In PbtA, there may be some prep for some scenes, but you then "play to find out" what happens with players and GM making moves that play off of each other in unexpected ways.
[MENTION=6696971]Manbearcat[/MENTION] is a great champion of DW. Perhaps he can do a better job here. I can do a passable job for BitD, as that's the PbtA ruleset I have experience with.
Well, it depends on what you meany by that. If you mean by "they must flow" that they mustn't contradict established fiction, we're on the same page. But in the Apo World play example, the GM determines the gender of an NPC that appeared in an earlier scene on-the-fly. It's neither pre-established nor derived from a prior Move.
I... I just... what? Are you serious with the gender thing?
I don't have any problem with blank spaces. Nor do I have a problem with inserting entities into the game world, on-the-fly, if necessary. However -and here's where we return to the thread of the subject- trad games have more rules that define the "physics" of a gaming world. Both the PCs as well as the NPCs are bound by the physics of this world. If the rules say you can only shoot one arrow per 5 seconds turn, that defines the game world to some degree. It creates limitations. Now this thread is about raising the awareness that to more closely emulate cinematic combat in one specific aspect (One-versus-Many) there needs to be a limitation to who can attack in a 5 second time frame. To be precisely, I am highlighting that within that time frame not everyone should be able to attack each round (not exactly a tough restriction). And if you are playing PbtA, you probably shouldn't narrate it that way either if you want to evoke a movie combat feel. In movie combat, members of the outnumbering force frequently wait to spot the opportunity for a single fatal blow. They also occasionally block each other.
Which trad game are you talking about? 6 second rounds is D&D 3, 4, and 5. Before that a round was 'some time' or '1 minute' and attacks in all are the effective ones, not everything that's possible. So, yeah, we first need to dispense with the idea that theses systems model physics rather than model a game. No D&D models physics or even models the fiction of the game world terribly closely. An 'attack' in 5e can be just about anything, fiction wise, but it has definite game mechanic results. My attack with a greatsword could include a feint followed by a half-blade grip thrust into a pommel strike, but it resolves as a d20+modifiers roll that does 2d6+modifiers damage. So, this the idea that 'trad' games model the world is silly.
For a cinematic fight in 'trad' games, you don't even need to change anything except the narration. Sure, all the gobbos get an attack, but the narration could be one or two stepping forward suddenly and landing a blow while the others jeer and taunt. Don't confuse the mechanics for the fiction.
Still, if you really want to do what you seem to want to do, you might restart your thread with 'How do I do this thing in 5e' rather than 'RPGs don't do cinematic fights well'. Many RPGs do it just fine, but they aren't D&D.