That's the speed of light in a vacuum. The speed of light in fiber optic is slower. Travelling half of the distance is not good enough, because if you haven't

That's the speed of light in a vacuum. The speed of light in fiber optic is slower. Travelling half of the distance is not good enough, because if you haven't received _confirmation_ of the purge, then you can't trust that it really happened. There could be network errors, etc. Sorry but it's not physically possible to do a global purge in 150ms.