Yes, I do this as part of my job.

I help manage a system that does something like this for a large network operator. We have test phones that run TWAMP, RFC 6349 and iperf (and a few other tests) on a routine schedule to special test servers. generating data which you will never ever see.

But you could do something similar if you had the desire. I have yet to see anyone do that yet.

All network providers have various throttling systems set up to limit your throughput, that is pretty universal, and, most of such systems are intentionally bypassed based for speed tests. They know the 5 tuples for all the speed test servers and bypass throttling for those test.

Yes, speed tests are rigged, think, Volkswagen Diesel, an inside joke pretty widely known in the industry.