Reach means next to nothing at the highest level
Yes, but none of them can utilize that advantage as well as Jones can. It's like how some people can hit harder than Anderson Silva, but that doesn't mean they can KO people like he does.
If I had to wager a guess, I'd still say Cormier manages at least a couple takedowns. Guy is beast mode when he gets his hands on someone. If Jones somehow manages to outwrestle Cormier, then holy fucking shit.
Many have tried to get inside his reach, only Gustaffson managed to do that.
You do understand that 13" of reach does not necessarily mean each of his arms are 6.5" longer, right?