It's obviously about latency. How do you not see the latency aspect of it?

Latency is directly bound by the speed of light. A computer the size of the earth's orbit will be bound by latency of 8 minutes. A computer the size of 2x of earth's orbit will be bound by a latency of 16 minutes, but have 4x the maximum information storage capacity.

The size of the book is directly proportional to the speed of light. Ever heard of ping? Does the universe you live in have infinite speed of light, and therefore you don't see how R contributes to latency?