Full speed means the speed the RAM is rated for. For example 5,000MHZ GGDR5 should run at full speed at 5,000MHZ. It shouldn't run at 714mhz
It’s not a moot point if you happen to be doing something that’s memory and bandwidth intensive like Ray Tracing just as one example where you need that full speed for the entire 4GB. Or if you run at Ultra HD you might need that full speed. Going down to 1/7 of full speed can under some situations cause a massive bottleneck over a similar product that has full speed ram for the entire ram. We are not talking as small difference here. 150 GB/s bandwidth for the first section and 20th GB/s bandwidth for the last section. As soon as you dip into that last bit of memory you take a large performance hit anywhere from 6% to as much as 85.71% loss in performance in extreme situations but on average its closer to 6%. How is it a moot point unless you happen to be fanboy? Its a major fact "some" users need to know before buying the product. Not everyone makes purchasing decisions on benchmarks, many make purchasing decisions on specs and in this case the specs are misleading.