This does not eliminate the cable as being a problem especially when dealing with capacitance. Capacitance is variable and only a small amount might make a difference like using input 5 which is on a different board and probably has slightly different capacitance. It can also be affected by temperature and age of cable. Temperature fluctuation is not usually a problem in the home environment and age might only change it a couple of pico-farads. But, if you are the edge of that digital cliff it can be enough to cause problems. When dealing with HDMI problems it I best to find out if it is an equipment issue or a cabling issue.
The easiest practical way to do it is by using short cables and test the system. As stated there can be problems with short cables just not as common. Most don't use this simple method because it is a pain to move their equipment near each other to test it but it can save a ton of time chasing your tail, trying different combinations of equipment or replacing equipment that isn't the cause of the problem. Other than trying different settings like 36 bit (12bit x 3 colors) to 24bit (8bit x 3 colors) it should be the first step in diagnosing HDMI problems.
The Key digital cable is not DPL certified and given its longer length I find it very suspect. There haven't been any cables over ~25ft that have passed DPL testing without some type of circuitry like Redmere or active cables.