What I was trying to do in bringing DW up is point to someone who is prominent in the 5e space who seems influenced by the game and has written a couple articles about it, and see if that sort of thing would qualify as a kind of mild boundary-blurring, shifting through technique some of the usual principles that might guide a 5e dm to something else. It seems that your response is, because it's not supported in a holistic way throughout the system, it would not qualify as a meaningful shift (or something to that effect?).
Okay, so your argument is that taking Fronts from DW, stripping out most of it except the list of dangers/dooms, and then modifying this using a different game's idea into a short list of the plot points a BBEG is going to enact on the campaign -- ie, just a story organization aide for traditional D&D Trad play -- is a major absorption of DW concepts into D&D? This is what you're arguing? Importing the idea of Fronts and stripping them down to planning aide for plot is importing serious stuff from how DW plays into 5e?
I mean, if we take a soccer ball, and using it to play basketball, have we significantly influenced the game of basketball with soccer? Because, you know, we've taken an important part of the game of soccer -- the ball (can't even play without it!) -- and we've put that in a basketball game. Sure, no other rules of basketball have changed, good soccerballs bounce pretty close to the same way basketballs do, and they're the same size, or very darned close. But, yeah, we've totes influences basketball by subbing in a soccer ball!
This is the argument you're making as I see it. It's saying "but we used the name of it, and we've like done 1 similar thing at the end of the day, so that's like, a lot, right?! It's totally a lot."
I don't particularly like 5e, it's just a useful point of comparison because it's so well known, and is incidentally what the OP's post was about. Aside from Blades, the game I'm vibing on right now is The White Hack 3e, but I feel it would be alienating to others to start talking about a relatively obscure game.
Anyway, your example from BitD shows, for me (can I emphasize that enough...for me) both the strengths and weaknesses of the gns framework, as I understand it. Since you buy into it, it allows you to identify what is fundamental about a system and understand how it ought to be played. It's prescriptive, in the sense that there is a more correct way to play any particular type of game. On other hand, I'm not sure it knows what to do with styles of play that don't line perfectly with its categories. Let's say there's a group using flashbacks in their 5e game...and, they're making it work for them. Are they playing it wrong? Is their game "incoherent"? Would they have more fun, objectively, if they didn't try to mix and match mechanics, principles, and influences in that way? I think my approach there would be to say, ok, if the group is having fun and making it work, let's assume they know what they're doing. Let's look at that as a legitimate playstyle, and then go from there, if we wish, to figure out what makes it fun.
No, they're not doing it wrong, but they've imported something that doesn't align with the other bits of 5e. This has been discussed. Flashbacks work well in Blades because they're so tightly tied in with the other mechanics -- they aren't free, for one, and they generate complications as regularly as other things. The implementations I've seen for 5e are pretty much just a plot coupon. And that can work just fine. The problem really only occurs when you suggest that they're the same thing. They aren't, even though they have the same name and you can "flashback" to establish something. The actual nature of the mechanics are vastly different -- a plot coupon is not a Blades flashback.
Introduction of plot coupons is an interesting thing in 5e. It very much depends on how these are implemented -- are they subject to GM veto? What is the allowed scope? How do they replenish? Are they tied into other mechanical systems? What do they cost?
As far as mixing and matching principles, you're making a broad assumption that the goals of play are the same for every principle. There are completely incompatible things, largely incompatible things, mehly compatible things, very compatible, and totes compatible. You're just idly speculating about generalities in what appears to be an attempt to claim there's no really point in looking at these things. What we don't have is any specific examples (outside Fronts things, which I've discussed) of the things you're trying to claim are easily possible. It should be trivial, if your gut is telling you true. I've actually tried. It wasn't easy. It didn't line up. I had to use fiat to make most of it work. If you're fine with this, cool, but you're already pretty far out of lane for Story Now (or Neotrad or Classic) play, so there's that.