With a properly triangulated 4 link, the joint ends will have some flex, yes, but not as much as would be needed without the proper triangulation.
I know Ryan is building that rig for the big stuff. But he's also thinking of maintenance too. While the proper angles and setup of the suspension will not need the JJ's, the rubber joints that's being used on that setup can be replaced for less than $10 each and can be had most anywhere. They also don't bang and clunk like JJ's do. So if he's in Moab and spits a joint, he can have a new one from the NAPA in town, fix it and be back on the trail in no time, for less than the cost of lunch.
A lot of time folks use a JJ to compensate for a less than optimal setup, let the joint take the abuse and make it work. A rubber bushing in that scenario won't last long.
There are several 4 link calculators online that work great. Setting up the correct geometry is key. If you're wanting to do something like that, there's a bunch of research to be had. But if you're cutting up your suspension and going that route, all the research will pay off ten-fold when your rig drives like a dream, doesn't squat when you take off, jump when you brake and doesn't wear out suspension components.
Ryan also doesn't talk much about how he actually sets up his suspensions. I'm not trying to be a dick or anything, so I apologize if I come off like one, really. I just know that Ryan has talked to a bunch of folks about how to do it and it's bit him in the ass. A couple of guys have even started doing it to other folks' rigs, getting paid, but when they run into a problem, act like Ryan OWES them something. So he keeps his advice to himself. Again, I'm not trying to be an ass at all, but I've known Ryan for a very long time. He's like a brother-from-another and I totally get where he's coming from.
Hell, I don't how to set up a 4 link either. I'd have to Google the crap out of it and even then, have Ryan up for a beer, maybe even some Macallan 18, and pick his brain.
Which reminds me, I need some Macallan 18.