Applying physics to those objeces would add a layer of realism to it, but for sure it will be heavy on the GPU/CPU. Let's say you have center stacked foundations and you want to extend some - how much you want to extend? What's the strength of the center foundation? What about if you extened 300+ and you break the foundation? The other 200 in the distance are not even rendered, not to mention to apply physics. It's too resource heavy.
Currently the physics are "Minecraft-way" - you place someting, it stays there no matter what (not counting gravel, sand etc.).
I was able to build on top of many mountains stacking 10-15 foundations on top of each other and removing the bottom ones to save resourcese (at the start at least).
I don't think they'll add physics for those kind of objects, but let's see.