The back surface of the drivers tends to oxidize, and it causes a white crytaline powder to form on the surface. Painting them helps to hide that. It doesnt affect their performance however.
Its less important for drivers that are hidden inside of a cabinet, but it can be a sore sight for exposed drivers, like those on the Mids of the X-Statik.
The paint looks like Duratex, and it looks like it cracked as it dried, i think the same happened to me when I coated the ones on my XLS in duratex as well, it ideally needs to be primed before the duratex is applied. To ensure better adhesion to the driver.