Yeah but katyusha doesnt have to get as close as pzwerfer does, in absolute terms, for the same radial scatter. Due to its longer range
People are greatly overestimating effects of range differnce.
Yes, pwerfer needs to be closer, but it also stays there only 25% of time katy needs for its barrage and pwerfer is more mobile.
Moreover, recent pwerfer buffs means you can stay at any range, target of the barrage will be annihilates with alpha strike, something that is pure RNG with a tiny chance for katy.