No offense taken at all. The solid color gray towel in low light is only trying to "simulate" low contrast to reproduce the problem, so that we can create a workaround solution until hopefully a firmware update can help improve this situation.
The conditions weren't with no light, it was with low light. It even struggled at ISO 10000 with low contrast.
Personally, I don't usually shoot towels in my bathroom either, as I tend to shoot action or sports and those subjects are moving quickly and/or wearing jerseys with numbers on them creating contrast. I'm also shooting under lights, poor lights sometimes but still lights. It's certainly more than mood lighting at a wedding reception.
I'm just learning the limits of the camera myself and trying to help others out. I would also like to add that initially I found the MKIV performed similarly to the 1DX under these same low contrast, Servo conditions, however the more testing that I've done in conjunction with the above techniques, I would now give a slight edge to the 1DX.
Wedding photographers shoot low contrast, slow moving subjects, in low light, and there seems to be more than a few that are experiencing this problem, and additionally Canon adds black AF points to their pro camera to top things off. Some of them also like AI Servo for their dancing or action shots during the reception.
I as well as many others, have found some ways to improve focusing under these conditions and they're listed in my post above. Yes, you can aim for faces, but a lot of faces and skin have low contrast too, especially with dim overhead lighting.
You could also aim for a dark contrasting hairline on a person with lighter skin. Aiming for the suit/white shirt border may be another solution. What has more contrast, your nose or eye, or a white shirt underneath a black tuxedo?
Some photographers were using Automatic and Zone AF in AI Servo, and they won't have a chance with those settings under those conditions. Their previous cameras seemed to have less of a problem with this, however this is an entirely new AF System.
Now, if the photographer can move the points manually to a contrasting edge, or shoot in One Shot, then the problem is greatly improved. Aiming for a contrasting edge will also help even in AI Servo! Some Wedding Photographers are actually using their 5D2 for the reception, and other experienced photographers have contemplated switching to Nikon, so it's a real problem.
So, if you would like to see if you got lucky and your 1DX doesn't have this limitation, then you could simulate my test above, if not then no problem.