The rear movement suspension movement of F1 car is not insignificant, the front is pretty much static, but the rear do have quite a bit(by F1 standard) of travel, if anything this is quite evident on the onboard shot. Which also explains that installation of inerter/3rd damper is primarily on the rear. While true that without seeing the actual location of suspension inboard pickup that its impossible to say what the kinematic may be, its not unusual I think to have a slight wheelbase change in travel especially if they use any anti-squat in the rear, which would mean slight inclination in the fore to aft pickup point of rear a-arm(or a-arms). A lot of the time too they might just do that so it can create a more desirable packaging for diffuser/rear wing/bodywork...etc, since 99% of the F1 design now is pretty much aero-driven with compromise to kinematics...