Wow. I'm a bit surprised at the person in the video, this isn't previously unknown. I've been aware of it for at least four years now, owning both versions. The account for the change of colour is true; the grey cart fixes a bug that prevents the two-player co-op mode from being completed with the black cart version. However, what can't be verified is whether this new version just replaced the old version at retail, or if they actually offered a replacement. The box shown in the video lends credence to the recall theory, as it looks like the carts they would ship out to those who requested a replacement. This is assuming it's legit of course, as I never underestimate how far counterfeiters are willing to go to scam people.
In either case, I have my doubts that the grey cart is any kind of rare. What I see this as is a guy finding a box full of an old game nobody wants, and finding a story that lets him sell them for profit. Making a multiplayer-only game on a system without online probably wasn't a smart choice, so the game probably didn't sell well in either colour.
As for the game itself, Turok Rage Wars has a bum rap for being a part of the Turok franchise, but it's actually a good game. It focused on balance a lot more than most shooters do, and that's probably why most people didn't take kindly to it because it doesn't have big, bad weapons and cheap tricks to exploit. You can choose five weapons to start with, two bullet type, two energy type, and one explosive type, and start with fifty bullets and must find ammo scattered around the arena instead of weapons. This limit means that each weapon has a more specialized use, good in different situations, so the selection lends some strategy to the game. The stages also have some nice designs, though many of them are pretty small, probably to try to keep the action up with the slow movement.