I would have to see it to believe it, because there is no mechanism I know of to account for it.
HDMI/digital cables in general are largely "snake oil," (quoted because of the common association, but certainly bears repeating) but they are not all created equal. I've found that they either let the signal pass as it should, do not conduct a signal, (defective) or present a degraded signal. (likely due to defect) While I hate to admit it, I was given some Audioquest cables (low end... I want to say Cinnamon?) and replaced my bargain-basement Rocketfish HDMIs. I immediately perceived a greater sense of depth/contrast on some random cable show, so I immediately called myself out on buying into a placebo effect and recruited my girlfriend to conduct a blind test the following evening. I had her trial me ten times: sometimes swapping the cables, other times not, and watched the same two scenes of Man on Fire. Amazingly, I nailed it every time -- and I'm pretty sure that part of my brain imploded when she told me at the test's conclusion.
I don't believe that story for a second. For multiple reasons.