Depending on the trim level of SS (eg. SS 1LE), the ZL1 1LE weighs as little as 100lbs more. I don't believe the 100lbs comprehensively changes the suspension requirements. SS models themselves vary by almost that much.
I agree aero, bigger/stickier wheels/tires play some roll, but when they say the rear wing makes 300lbs of downforce at 150mph, the suspension still has to work in other corners. There aren't a lot of 155mph corners out there and the downforce is likely close to half in a 80-100mph corner, let alone a 50.
There's no question that different suspensions are tuned for different purposes. Part of the magic of the DSSV and magnetic shocks vs. conventional dampers is that they can be tuned to behave differently in different situations. I recognize how they've described Milford and I've read that stuff before, but part of me wonders if Milford has some bumpy sections that are not conducive for the DSSV shocks, almost like a general handling course...
Seriously though, did you read that laptime vs. suspension chart and think "just as I would have guessed?"
