Ah yes, there is a difference after all. I was holding the MBA up to my ear and clicking with the option on and off and couldn't notice anything, but after putting it down on my desk and trying it out there is a definite difference there, but it's certainly quite subtle.
I did read someone's theory about the smaller trackpad in the MBA being the reason it's there because the taptic engine is (or was) the same on the Pro and it wouldn't have the same effect with the larger trackpad on the Pros. I've never experienced it on the older devices but I have seen a few people saying it did make quite a big difference.