As someone who's been using the wowhead modelviewer frequently since forever, I ask for some proof. They have some animations that have been developed for Kultirans (as you seem them using them in the trailer) that are usable in any character (since they now animate using a universal animation rig). They include some walking animations, carrying kegs, guard posture, etc. You can make an orc use those animations (and appear to have a straight posture). But the wow modelviewer does not have the animation that is going to be made live for straight back orcs. That one hasn't even been implemented in alpha yet.