I’m going to tackle one of your questions first.
Shock-proofing is most important when the rotating mass is high and the likelihood of shock is high. An example would be a large balance wheel on a slow-beat pocket watch. It’s quite common for balance wheel shafts to break in this sort of watch.
The escapement wheel is small, extremely light, has very low inertia and I have never experienced or heard of one breaking its pivots. I've seen plenty of broken balance shafts
I’m sure JLC based their decision on reduced cost of materials and labor, as well as the effect of making the movement thinner.
Cazalea