(Not the anon you're replying to.)
Your arguments do sound logical. Long bones don't sound ideal for blocking kicks, and sure some have got broken that way.
But at the same time, I remember myself blocking the kick of a savateuse that way in a savate class. by accident, shin blocks are illegal in savate. I'd been cross training in Muay Thai. It did work. Unfortunately she got hurt by the block. I wasn't meaning to do it, the cross training just came out.
(Another unrelated observation. First day beginners often do well in savate sparring! They tend to do unchambered kicks like football kicks which can be fast. They're like the old "defense dans la rue" system designed for street self defence.)
I guess a lot is going to depend of the angle of your blocking shin (if it's angled, knee forward maybe that's what dissipates the force of the incoming strike along the long bones of the blockers shin?), relative bone density, etc?