No the small waist & hips and tiny joints are more to do with being symmetrical which he stood alone , but as far as structure his was not special not like Paris , Reeves or Cormier , he was narrow but it wasn't as obvious as Heath because he has such small waist & hips.
Reminds me when Nasser was commenting on his contemporaries
Flex Wheeler, at first glance, seems to have a balanced physique.
People do talk about his nice lines, but he has them because some essential muscle mass is missing from his frame. For instance, when he does the abs and thighs pose, his lats disappear. Take away his arms and you are left with a juvenile body. I am 511 and compete at 285LBS; Flex is an inch shorter and competes he says at 224LBS, but I think he is about 10LBS lighter. He has a small waist for sure, but he also has a big butt and narrow shoulders, just like Shawn Ray. Check abs shots of both of these guys. I call Flex the Lord of Illusion.
Sorry but I'm not taking the word of" Bitter about everboty " who beat him as the gospel. I'll use my own two eyes.
He had a great frame, Structure is more than just the width of your clavicles, those are two bones in your body out of 206. Joints, limb length, bone thickness and shape are all part of your structure, as is the way, and the where... your muscles attach to your body, they attach to bone via ligaments, and the shape and placement of these bones, along with your muscle bellies,and they way it all fits together determine your appearance. it's all part of your structure.
The only one of those guys you mentioned with a better structure than Flex was Cormier, and he lacked roundness and that 3-d "pop" to his muscles. but his structure was perfect.
PS "small waist and hips" is part of your structure, or do only collarbones count?