Actually… a choice for bulkier build is expected in the game, even though it was not included in the preview.
Tina: You are all going to be in Dracthyr form when you are in combat. Yes. But let me talk about the Dracthyr and their customizations. There is more customization than what you saw in the video. there’s actually so many ways that you can customize that Dracthyr. Even the shape of the face. You can have, like these snouts that can look more ancient, or more sleek, or like a more blunt.
You can even slightly change your torso to be like slightly more slender or slightly bulkier; and the armor that you wear is a type of armor that you will be able to customize at the Barbershop, too. So Dracthyr, I think they’ll also be able to wear shoulders, tabards, belts across their visage and Dracthyr form. While the visage form is able to wear all-armor.
Full article: https://warcraft.blizzplanet.com/blog/comments/world-of-warcraft-dragonflight-interview-with-jackie-wiley-and-tina-wang
Or on wowhead: