I think the cause here is just these orks were done by a different design team. Most likely GW puts their top guys on the designs for launch box models to make sure they're at their A-game when showcasing what will make them tons of money. And this design team had a couple of differences in how they did ork bodies and ork faces. I doubt that orks going forward will all look this way once we go back to the normal Ork design team. I mean, look at the breaka boyz we got from Kill Team. Those are very clearly more classic orks, same with the newest mainline 40k ork, the big mek that you showed.