Nick Walker does have great form but isn't he using mostly machines? It's much easier to have picturesque control and form on a machine because there's less to control. A machine movement's path has already been established, it's non-negotiable unlike a barbell or dumbbell.
I will answer this with a different angle; the most impressive thing I've ever seen from both a strength perspective and also a form perspective was Stan Efferding handling 5 plates on the incline press for five reps. Larry Wheels the same. Stan had excellent control and considering how much weight was on the bar, I'd say the negatives were decently slow from what I recall. Lee Priest had great form from what I recall as well and handled very heavy weights at one point in both free weights and machines. Haney had good form but never used particularly slow negatives (not that that's the end of the world but it certainly makes a rep harder). The criteria by which I'd base my answers on for this question would include whether using free weights or machines (you know which is harder to have good form on and this isn't saying which is better but certainly one is harder in terms of control), amount of weight, and the time it took for the eccentric portion of each rep.