My deads are quite round. Used to not be able watch a video of me deadlifting, it looked terrible (feels absolutely fine, though). I have widened my grip over the years to compensate and keep the back straighter. Allegedly it's sub optimal for weight but I've found that it suits me. I suppose if you feel safer, you pull harder.
I think there's a rounded back like in the vid and there's hunching up and forming a leverage point at your mid back and loading everything through that.
Is it just the upper back that's rounded? I have a bit of kyphosis but my lower back doesn't round when lifting. Some demand everyone must have a perfectly straight back but peoples natural postures differ and it may not be harmful to lift as you're built. Google says there's no such thing as the "right" posture
Konstantin Konstantinov had that rounded upper back which some noobs criticized but he was just built like that. Here on that brutal banded deadlift.
Having a wider grip might not be suboptimal for some as far as max loads, it might turn on the quads and actually help, sort of like some have stronger floor deads compared to racks. I have tried snatch grip deads because I've tried everything. Knees get in the way and it may feel awkward but perhaps it could be helpful. Deficit deads and snatch grip deads help if someone has a hitching issue. IME you almost
can't hitch when doing these.
