To this day I still consider this the nerf Genji needs. Like the OP said, it doesn’t make sense why an ability as powerful as Swift Strike gets a free reset on an ultimate that, with or without it, proves to be the most powerful ultimate in the game. It allows even poor Genjis to align themselves into ideal positions that will be hard to fight against, allowing Genji to gain momentum with an ultimate that is balanced around the difficulty of getting that momentum.
As I’ve done so every time I mention this nerf, I’d like to point to Bastion and Configuration: Tank, an ultimate that is effectively the same as Dragonblade in what it does, except it’s worse in every possible way. Where as Genji can move while popping his ult, gets a free dash reset, pierces barriers, can be combined with two abilities that greatly compliment the ult, gets enhanced move speed, cleaves, and is still allowed to move while the ult deactivates, Bastion gets penalized. Bastion is not allowed to move neither before or after the ultimate despite having a longer cast time and no mobility, Bastion gets a difficult-to-handle projectile weapon that requires direct hits to get value, the ultimate is easily blocked by barriers or simply breaking LOS, Bastion can self-harm with it, and other than that, only gets the same damage reduction they’d get for being in turret mode.
And I think we can all agree that, even outside of their ultimates, Genji is objectively the better hero all around. So even despite being a better, more usable hero in every other regard, Genji also just gets a superior ultimate that’s full of forgiveness. Meanwhile, Bastion still has to deal with the no-fire bug on their first ultimate shot.
This, among other reasons, is why Genji doesn’t need a dash reset. He already has fantastic tools for getting into position to use his ultimate, it’s easily one of the best ultimates in the game, and it’s an ultimate that’s very easy to enhance with team abilities like Nano Boost, Zarya bubbles, Lucio’s speed boost, or even just a standard Mercy damage boost. I don’t see any reason why Genji needs extra special treatment and gets a free dash reset, it would be a slap-on-the-wrist nerf considering it would still be just as deadly in the right hands, it would just mean that Genji doesn’t get a bird’s eye view of the battle for free to allow him to pick a target to ensure a kill on.