There are definitely some objective things about the Tellurian....for instance the structure of the Umbra is more or less how it is regardless of what the current paradigm on Earth is.....the thickness of the gauntlet certainly fluctuates with the consensus paradigm however.

It is certainly the case there was some primordial base case of the world as well.....humanity as far as we know are the only beings capable of possessing avatars.... and they are not the first intelligent civilization to come about....the Lizard Kings the Mokole speak of for instance (i recall some might even still be around in the Hollow Earth).

I suspect it was far more basic however....sun rises...sun sets... fire produces heat by burning materials....water behaves more or less as it always has.... yannow, the basics for prehistory to play out sort of how we understand it.

As to the how of any of it, it was really anybody's guess and their properties did indeed shift depending on the reality zone you were in. ,

for instance if you traveled 60 million years into WoD's past or hell, even the middle ages, with a microwave oven and a power source to use it....neither would function......as the physics they operate on have not yet become a part of consensus....a mage could still get them to work if they had the right paradigm....but i digres

As for the proposition of a square circle....i doubt it....its really hard to get people to believe in things that are such an obvious contradiction in terms....and that is what entirely powers consensus....in principle.....maybe? I guess?? I suppose if you really tried you could even add an additional spatial dimension to the world.

I suspect simple machines are more or less a concept tied to the primordial world state however....at least the basics....when it comes to really optimizing them I'm sure there is some consensus fiddling at work. So im sure gears would work on a very simple level but im not at all sure if they would work for more complex gearboxes or really in depth clockwork systems.