You can do that sending while you're waiting for the disk to provide said GiBs. I also believe that useless uses of cat are often acceptable for readability (many novices are not familiar with redirecting standard input, particularly not as the first thing on a command line).
Who said the GiBs need to be fetched from disk; they could already be in RAM. Even if not, it's still adding many system calls and context switches when the CPU could be doing other things; the machine isn't running just this one thing.
It's not that simple anymore... In modern CPUs, NOPs are discarded by the decoding units so they never occupy the exeuction units. If decoding BW is not saturated (and most often, it's not), NOPs are indeed "free".
