Depends on what you mean by "impulsive," I guess.
There's impulsive in both suddenness and act. Eg, someone gets dumped, and shoots themselves. They could've been totally fine prior to that and then without much thought they attempt or complete suicide. This one is totally impulsive according to both outside observers and the person attempting the act.
Then there's just suddenness of act, eg, someone who's been depressed for a while suddenly attempts suicide after some event which finally drives them to act, but they've had suicidal ideation for a while. This one might appear impulsive to outside observers, but isn't super impulsive to the person attempting. This was me when I had my first attempt. I'd had ideation daily for months. I'd not only wonder what would happen if I rode my bike out into traffic, I'd have to fight the impulse to do so. But when I finally attempted it was not well thought out, and I made the decision in a single night. I tried a method that had, I'd heard, killed a friend. And it didn't work for me. I was completely ignorant to how difficult it is to actually succeed, especially with methods where instinct has a chance to kick in. My attempt and my depression weren't less "real" for that fact; I just didn't know what to do with what resources I had on hand, essentially.
It's hard to say what's "real." There are certainly people who intentionally don't act with severity enough for it to be fatal. And there are people who fail because they don't realize how much planning this actually takes.
I know the cynical part of my brain, this time around, thinks people who commit suicide suddenly because they feel they'll never get a date or something are really silly, for lack of a better term. Like, the kind where they genuinely haven't been struggling for months, and the reason is kinda shallow (I see this a lot with like, 18-23 year olds and I'm just thinking, do you even know how young you are and what a weird snap judgment that is???). But mostly I try to keep an open mind. I never really know what people are truly going through.