But with a 4 link like the one pictured, its hard for me visualize how the short uppers arent affecting the front to back motion of the axle?
Here are pictures that might help visualize how only the lower really matters for front-to-back motion. This graphic assumes the lower is literally at the center of the axle tube which is impossible, so the uppers do matter a little bit, but for any logical 4x4 build the lowers are way more important for wheel-base/front-to-back motion.
These are two totally arbitrary suspensions (not modeling the Evo suspension at all), one with logical upper/lower lengths, and one with uppers that are insanely short compared to the lower.
Here it is at "ride height" showing the pinion angle (depicted by the short vertical line above the axle tube) is the same as well as ride height:
And now we droop out the suspension. Because the lower links are the same length and at the axle tube, the wheel-base and front-to-back motion are precisely the same, only the pinion angle is screwed up due to the short upper links. The anti-squat is also shot through travel. But the wheel base is unaffected and the rear-steer is exactly the same between the two suspensions.
I'm not saying upper length doesn't matter, it's critical to have appropriately matched upper and lower links (usually uppers should be just a bit shorter than lowers, but it depends on the suspension design plan). It just doesn't much matter for wheel-base effects such as rear steer.