The patent is not on haptic feedback. The patent is on a very specific means of implementing haptic feedback using ferrofluids and electromagnetic actuators that it is claimed (and Apple deemed it good enough to copy, so presumably truly) allows for both a smaller implementation than typical mechanical haptic feedback (i.e. the off-balance-flywheel approach of phones of old), while also allowing for low- or zero- noise compared to “speaker or piezo” based haptic feedback.

There are a lot of shit patents in the world, but on a surface reading at least this seems sufficiently novel that I don’t see why it should be invalid. One also presumes that if Apple had any grounds to invalidate it on prior-art they would have done so.