Interesting question, not being negative Nancy.
First to all, the reason for swapping to RX8 knuckles is reliabilty/safety, since it is well known from the Pirelli TCR class that the original MX-5 hubs are weak. Even the new MX-5 class allows and recommends the swap.
With that being said, I did see a "gain" in camber. I would put it as non-conclusive since I removed all the links and eccentrics when I swapped the knuckles. The "gain" I saw is easily achievable with the original hardware. The only way to really know is to measure both knuckles. I would be surprised if it hasn'