(If you want the tl;dr, just skip to the part about knockback influence(KI).)
Regardless of what we call it, "Vector or Vectoring" is not the best way to name it. Here's why:
1) Those terms are too technical. When we name something we should try to convey the concept of it in layman's terms. Names like "short hop", "fast falling", "air dodge", "spot dodge", and "edge guarding" are examples of good naming. If you were unfamiliar with "short hopping" and hear it, you would assume it's jumping but shorter. When some people hear "vectoring", it means nothing to them. Even people some people who know what vectoring is will have a lot of questions still. @
Chiroz
argues that it takes a few seconds to google, "vector", but that is too much. You don't have to look anything up to get the concept of a "short hop". Having to look something up breaks up a natural in-person conversation as well. It just adds in extra questions in between finding out how to use the mechanic. We can name it such that it requires no technical teams, so why have the extra step? We should name things as intuitively as possible. This new version/replacement of DI is easier to grasp, why give it a more difficult name?
2) Looking up the terms "vector" and "vectoring" I get(From Google search: "define vector, define vectoring":
Vector: a quantity having direction as well as magnitude, especially as determining the position of one point in space relative to another.
Vectoring: direct (an aircraft in flight) to a desired point.
This new DI definitely involves vectoring. The problem is that so does the old DI. You change the trajectory, but essentially that results in changing the vector. Just because speed/magnitude in this case does not change doesn't mean it doesn't have it. Arguably all movement in smash is vectoring, whether that is running, walking, rolling, or jumping. You are moving towards a desired point. The new replacement for DI is not the only instance of vectoring in smash, and it would be misleading and potentially confusing to name it that.
3) Calling it "vectoring" makes it sound like it's an exploit or something that's not supposed part of the game when it's clearly an intentional mechanic. I know this one sounds really silly but we've all seen the people hating on wavedashing that clearly don't understand what it is. We all know how many people still think it's a glitch, and I wouldn't be surprised if people think the same of "vectoring" if we call it that, as little sense as it would make. It really doesn't sound like something you'd ever see in the instructions of a game like this.
Personally I think the best choices are
keeping DI, or using
Knockback Influence(KI).
The case for DI:
1) The most obvious reason is that it's already an accepted term. To a lot of people DI simply describes the phenomenon of holding a direction to alter where you end up during knockback. When people say things like "DI down", in this and previous smash games, it still means hold down on the control stick. It still serves the same purposes. You hold a direction so you survive longer, or to escape combos/strings/followups. Even though the implementation has changed and knockback is altered in addition to direction, the term still works.
2) "Directional influence" can be adapted. Terms don't have to mean exactly what they always have. To a lot of people "L canceling" meant pressing L to cancel landing lag, but it seems that now the more accepted version is that "L cancel" is simply short for "Lag cancel" since it can be done with any shield button. We call tilt attacks tilts, despite the fact that you aren't really tilting a 3ds slide pad, you are just sliding it halfway or slowly. The term still works if people know what you mean. It still makes sense to say, "directional influence is holding a direction to influence your knockback in terms of trajectory AND speed".
3) But won't people get confused if we call it DI and it works differently in the different games? No. Plenty of things work differently in the different smash games. Air dodging, Smash DI, grab releases, ledge mechanics, hitstun canceling, and many aspects of the movement. Things change, things get revamped, that doesn't mean everything has to be renamed. An air dodge is still an air dodge in this game, but we acknowledged that they are quicker and have landing lag now, just like how we acknowledged that they were no longer directional or caused free fall in brawl. Our mechanic for having some control over our knockback has undoubtly changed in this game, but it has arguably been revamped or overhauled and not replaced.
4) Funny enough,
if you look up "vector" on thesaurus.com, it returns the following words as synonyms: "trajectory", "direction".
The case for Knockback Influence (KI):
1) I think this best describes what's happening. It's direct with it's name, and works semantically. "Knockback" is a level above direction. It includes direction while also including the other relevant things to the mechanic like speed so it's perfect. It also right away tells us that we're referring to the knockback itself. With DI or Vectoring, you might at first think that plenty of things in this game involve directions and vectors or vectoring. With "knockback" influence it intuitively implies what you are influencing to more detail(the trajectory and/or speed of your knockback). It conveys the most information, and it does so in layman's terms. The only downside I see here is getting an entire community on board to adopt this. Also it sounds like Killer Instict, but come on.