What I understand from the articles is Mercedes and Nissan uses two different techniques to safeguard the paint. Nissan uses a more elastic resin clean coat which flows back to its original shape easing minor scratches and Mercedes used a tougher clear lacquer, which contains microscopic ceramic particles which hardens when it dries in the oven, forming an extensively cross-linked network.
Anyway, according the article, mechanical car washes are the main reason for these blemishes. I have seen enough muddy coloured automatic car washing wheels in so many places. So try to avoid these Automatic car washes as much you can.