Your misunderstanding and a lot of peoples on this thread is that the bit that you have a
problem with is part of the disk; it’s the outside diameter of the wheel mounting face of the disk. The hub is something that you won’t ever see - unless you remove the disk.
I do see where you are all coming from on one side but its just something that has never bothered me… apart from the aesthetic issue there is no detremental effect of this surface rust.
Something I have noticed though, my last car (MY03 Toyota) had the same
problem. I do some work at the manufacturing plant in Derby sometimes and have noticed that the part of the disk that is rusting on the Leon is now painted with a lot better coating than it used to be when I’ve walked through the plant previously - whether this has made a difference in the real world after exposure to the elements I honestly don’t know!?