We can elaborate this idea further. Why did they have such a short wings then? I see two possible explanations:



A. The atmosphere is much more dense in Heaven. If this is true then, for example, when angels open portal to Earth it would be immediately surrounded by clouds due to rapid expansion of incoming air and, therefore, cooling down - kind of explains why the Heaven was thought to be up there in the clouds.



or



B. The gravity in much lower in Heaven. This does not match the story well, however, because then humans would be physically stronger than angels. However, angels might be perceived stronger just because they used advanced weapons, so it's not conclusive.