You did not miss it, it isn't in there.
Almost every single first drive event is pre-production, didn't think it needed spelling out.
Why? Is there some glaring issue that requires highlighting?
The glaring issue is the company often, as in almost always, throws a TUNE on the motor in this category of vehicle.
What are you basing that on?
I have mentioned this before...I had a friend who worked in the dyno room at Ford and it was his job to do precisely this for press cars. But it was far, far more than a simple tune. Every single engine component were weight matched perfectly (all pistons, connecting rods,valve train etc). All flash was removed from any cast areas to be perfect. And the list goes on and on. While everything was indeed OEM, only the most perfect components were used off the line and the engine built as perfectly as an OEM engine could possibly be built.
Do I know if other manufacturers have done/do this? No idea. Would I be surprised if they did this? Not in the least. Do I think this practice still goes on? Yes.
I've read about Ferrari being fanatical about this type of stuff. Bringing 1 car for drag strip duty, another for track duty. Having to know the track ahead of time so that they could "prepare" the car. The weird thing is, why on earth did they bother? Things a freakin' Ferrari! I doubt folks would choose to buy a Z06 because it turned out the Chevy was a couple of tenths quicker around Streets of Willow. Do people even cross shop exotic cars?
Same thing applies here. What on earth is the MX-5 competing against that they'd have to tune the car? Also, what possible gain could they get out of a stock 2.0L motor?
Lastly, if you are
too good at tuning the cars, you end up embarrassing yourself. Because owners can dyno their cars too. I know this happened a long time ago, but in 1999 Ford looked kinda silly with the SVT Mustang...
It is this last item that makes me suspect that there isn't a lot of tomfoolery going on with the cars. If you constantly had pre-production units offering performance that couldn't be matched by the retial versions, there would be hell to pay. My only concern with early products is that they give an inadequate/inconsistent impression on polish/NVH.