I know the aftermarket wheel bug is fixed. However, this makes any car that has wider rear tires and is fitted with aftermarket wheels more controllable. This is not an MR-only thing.
The unofficial bug fix list however states that handling of MR cars is fixed. By now I think that is false. At the very least there is no conclusive evidence or a significant amount of claims (compared to the claims stating otherwise) to back it up.
The problem with these claims is that there are always people who see or experience it too. People are easily influenced. If I were to state that 'rosso corsa' looks slightly richer and deeper in 1.03 I am sure I'll find some people who see it too
I am not saying they absolutely didn't do anything about MR cars, but there is just no evidence at the moment to say they did.
Maybe it would be better if @
Terronium-12 took the statement about the MR cars being improved from the news section.