I was thinking the same thing.
Chickens do spread their wings one way in hot weather as they pant, and they huddle in with their feathers fluffed in cold weather. So if his pose changed a bit as the weather changed, it might just be his way of dealing with the temperature. But if you are seeing matching poses in both hot and cold weather, it more likely points to something else.
In general, that body posture goes with a chicken that doesn't feel good (that overlaps with being cold, because being sick or hurt will often make a chicken feel cold too.)
One way to check if he feels cold: provide a warm area and a cool area and see where he chooses to spend time. Something like a heat lamp in one corner of a big area would work as well with a chicken of his age as it would for young chicks, letting the bird choose the temperature where it feels comfortable. (Not saying you need to do this, just that it is one possible way to check what temperature the chicken likes, and whether the body posture is temperature-related.)
