The Mk8 has the same basic suspension design as the Mk7 and Mk6, with only incremental changes like stiffening the center of the torsion beam, different sway bars and the upgraded front control arm bolts. Barring the change in engines, bodywork and stock wheel/tire sizes, all 3 are actually remarkably similar chassis.
The Mk8 force vectoring springs, while they are supposed to reduce side deflection of the rear suspension arms and make the car feel more stable in corners, they are not “critical” for the suspension to work. Your aftermarket springs will work just fine and won’t damage the car, so there’s nothing to worry about, unless you just don’t like the H&R’s
Interestingly, there’s also no reason I can find that would prevent you from installing Mk8 force vectoring springs on a Mk6/Mk7 or US model. The only reason not to would be that we simply don’t have good info on the actual spring rates compared to the Mk7, and if the weight on the Mk8 has changed significantly, the ride height might be off (also 2 door vs 4 door usually means more rear weight, so slightly different spring lengths)
I do suspect based on Ford’s tuning approach (stiffer sway bars and torsion beam) that they also went with softer springs, much like the mk7 to Mk7.5(ST200) changes. Softer ride with higher roll stiffness to compensate. I don’t have any evidence to support that, just a hunch.
