Soundness is made out to be way more complicated than it is. They can either move around or not. It's kind of like trying to compare the walk of a runway model to that of female track star. One might be prettier to look at on the move, but the other one gets there just fine.
With the exception of obvious cripples, 99.9% of people that look at an animal and say "this is causing that" or tells you how much worse they are going to get with weight are talking out their rear end and its just a guess. I've had ones I thought were perfectly sound blow up and calves that were criticized for being too straight at every prospect show wind up doing very well at their terminal majors.
I have one in the barn right now that probably isn't straight enough. He's the thickest steer I've ever had in the barn but the best way to describe his walk is "knock-kneed". Takes perfectly long strides, but not pretty to look at from behind on the move. But he could probably outrun a quarter horse.
In the end it just depends on the judge.