The jacket in the lighter caliber's is not as thick and allows for more rapid expansion. The way bullet design was explained to me was that a thicker jacket would hold together better and allow more penetration. Again IMO this is why you have premium bullets-the premium bullets are "supposed" to be of better constructin, so they will hold together better for better penetration. I am sure you have heard of light, fast, small caliber bullets blowing up on a shoulder. I realize part of this is bullet tip design. But a lot of it has to do with the jacket to allow further penetration.
Not sure if there is a correlation between lightweight Deer Bullets and larger caliber deer bullets as far as jacket thickness goes ..I guess I will have to get out the bandsaw and cut some up. .I do know for a fact that I can get stoutly built 257 bullets from at least 4 sources if not more and all will not hand grenade on a deers shoulder or other area of resistance. Another relevant point is Deer are thin skinned animals ..break the skin and even a bullet that is pronte to separating will penetrate sufficiently to cause massive internal damage at the same time delivering shock to internal organs. NOw if we talk Elk or similiar sized creatures then you have less room for error in the bullet selection process.