Actually the Lefevers have much more solid wood behind the receiver than most other sideplate/lock guns. Drew Hause's photo abover shows this. L.C. Smith might have some of the least amount of wood out of them all. Crescents and bakers have a bit more than L.C.'s but not much.
As stated, not as many Lefevers are broken to bits than others, and I think it has something to do with the fact that there is more wood in the front. And this is mostly to do with the fact that they are not side lock guns. Since the hammers are in the frame up front, the stock needs a lot less wood removed for clearance of moving parts.