That isn't true, moving in a bait fashion leads to sure headshots and such. I've done it for years, usually close range stuff.
An other lil tip that I'v been doing for years and saved me many times was a proper E usage. I know, it's not "footwork" but it's something every gunner should master, mostly in an evasive manner (Offensive is the most obvious and easy thing). For instance, while running away using an E to get a high ground but actually holding shift midair and bait the opponent there. Using corners and movements to mislead them and make them think.
You got the idea, map knowledge and stuff, yada, yada, yada.
Dueling is fun, no doubt about it. There have been days I sort of craved it, because it's satisfying. But, it doesn't prove anything. I've seen snipers being absolutely trash at duels but being a game changing resource. How that is? Probably because of the decision making on the target choice, not hunting any specific impossible shot, going for sure important kills. I've seen many of these guys, crafting a differthing kind gunner. Maybe them being able to face better a gunner would make them more efficient than they were already, or maybe not. This can't be proven, in any way.
With that being said I'll just add a few details about duels. You could use the buggy game design to your advantage, by making unable the enemy to get a hs (It's an actual thing, I think i showed nico few of them months ago). You could just get mid-range and no-scoping by keeping an unusual faster pace. You could slide abuse properly and never being easily hittable. You could corner peek and so on.
Some of these might sound completely scummy and unfair, some appropriate. But they all have been and are viable styles, all really effective. None of those actually require any great aiming abilities, just being able to throw the enemy off enough to let you hit more than he does.
I have personally used few of these (not often in the few duels I've done), that's how I could dodge many snipers at once (if I do it now I'd probably fail miserably), even if few of them were considered really good ones. I still remember @Zeretly_Myzery being astonished by the way I could face him and goku at the same time years ago. That specific event didn't make me a better sniper of both of them. I just learnt while dying the first few times, what they used to miss and what they didn't and used that knowledge against them. That's all it took. They probably even had a better aim overall than I had, which is hilarious.
Duel never proved me anything about an other gunner skills, beside some bad aiming practices (which I usually notice them and try to help 'em to sort those out lol).