Well, I mentioned it because they're SAS cables (and quite old ones) for disk shelves, not ethernet cables - their rated speed for the application they were sold for is 6gbps per channel, and 40gbE is nearly twice that. Like I said though I'd imagine it would still work given they're not crazy long and you have good transceivers on both ends (eg not cheap switches/cards)
I think you'll be the first one to try out the 15 foot long version, so post your results somewhere so we get STH in google results for even more niche questions