Lots of people training a running dogwalk are under the impression that if the dog's back legs are split apart that they can't jump and they use this for criteria. Take a look at this video at around 27-28 seconds.
I can't speak for all dogs but my dog can take a nice big leap with his rear legs apart. And good luck spotting that while you're training. You can check for it on video after the fact to decide if you've been rewarding properly but it's not practical criteria for the training field. And as Strummer proves, this criteria doesn't work for all dogs. As always it's important to look at your dog and adjust your training accordingly. I gave up on that split leg theory ages ago because I could see it didn't apply to Strummer.