If you have ever had a grill shell out of the vehicle, the last term you would use to describe it is flexible or a little bit flexible. It takes about 30 seconds of examination, a bit of critical thinking, and a small bit of knowledge about material strength to figure out that anyone who says the TJ grill flexes is pretty much full of shit.
Look at how the OEM radiator is mounted to the mounting flanges. The two plastic end tanks have small recessed areas molded into them that a #10 size machine screw with a square head is slid into. There are two at the top and bottom on each side in the slots. The mounting flange has holes that fit over the screws and then a Keps nut is threaded on and tightened down.
If the grill shell flexed, it would rip those tiny little screws right out of the plastic. Of all the issues and problems I've read about over the years, the failure of that attachment method has never been brought up or mentioned and I've never seen it on any used radiator I've messed with either.
The other thing that is overlooked is how the grill is mounted. There is a center mount with two snubbers at the outer corners on top of the frame. As the frame flexes under articulation, one side moves up and compresses the snubber and the other side just lifts off the frame since the shell can pivot on the center mount.
I know from a design failure that if you try to mount the shell to the frame at the corners and eliminate the center mount, it will tear up the mounts, or rip the bolts out of the corners of the shell and even then, it won't damage the radiator.
As for the 4 bolt mounting. Take a look at the flange sometime. Once you figure out that the flange is about 3" wide and unable to flex laterally since that is a very large shear plane, you'll understand that 2 bolts, 4 bolts, 6 bolts, or 20 won't change anything. It should be noted that the 05-06 that come to us leave the factory with 2 bolts per side. I suspect that is not because there was an issue with damage but because they figured out the flanges don't flex and it only needs 2 per side. The reason I think that is we have seen quite a few with just the upper bolts holding them in. (not recommended)
Was passing on what I was told from rep. I didn’t have enough knowledge on how core support was built to argue the point. That’s why this form is great so we can get it all out there and decide what is best