I think that there is more to the pool of information than the points you rightly outlined. Other key pieces of data are that Redis is designed to be extremely fast and that it has a strong reliance on the speed of the memory it is operating on. Those facts, coupled with the statistics sniglom mentioned above, very strongly indicate that performance will be terrible.
An analogy I can think of is testing if a stock Ford Fiesta can reach the speed of sound. You know what the engine is capable of, the environment it is operating in and the tires it is running on - you simply don't need to floor the accelerator to come to a conclusion.
That saying about picking ones battles comes to mind. The mindset is certainly of a sharp character, but what good is a knife without a hand to guide it? The map is not the territory but it does save a lot of time if used strategically.