^ HDMI operates constantly on the edge of failing. It is simple, twisted pair wire with inexpensive electronics at each end. Its roots go back to DVI, which was cabling for connecting monitors to computers that pretty much pooped out beyond 10 feet.
One of the goals of HDMI was to extend that length -- but still with cheap electronics. That was done by adding re-equalization into the transmitter and receiver chips to counter the degradation in the signal as it travelled down the cable. This has become more sophisticated in later versions of HDMI, but it is still pretty simple, and the big simplification is to design in a base level of correction for the EXPECTED change in the signal.
And that's built around a 6 foot length.
So if you use a short cable it overcompensates.
The symptoms are the same as using a cable that's too long -- more HDMI handshake failures.
Just as some people have good luck using long cables, others have good luck with short cables. Using 6 foot cables merely maximizes your luck.
This becomes more important if the HDMI chips handling either end of the cable are of different vintage. Indeed it used to be that problems were common if the chips of the SAME vintage came from different manufacturers. If both ends use today's new chips such mismatches are much less of a problem these days. But there's still lots of older gear out there.
Anyway, using 6 foot cables where possible is sound advice, and much less messy than drawing a chalk Pentagram around your equipment.