Looks like more research is needed. The current films available (3M, Suntek, Xpel, etc.) are much better than they used to be 10 years ago. I found this quote from a PPF/tint forum, posted by a distributor in 2017:
A majority of the time it's discoloration due to the film just being dirty. It's more prevalent on white than any other color which is why it stands out more. But none the less, the film is just usually dirty from poor maintenance. The problem is when the products are pores, they open and close from the exposure of heat and sun which causes the elements like dirt, debris, pollen, chemicals, etc... to soak into the product and therefore get locked in if the surface isn't maintained. I think we as an industry wish the films were self maintaining but they aren't and will always need some type of maintenance. We are seeing more companies add coatings to the top of the film to help with that type of defense and utilize PPF as more of a chip protection to the paint.
Meaning, once you get the PPF installed, you maintain the PPF just as you would the paint. Clean it every once in a while, make sure it has some form of UV protection (wax, sealant or ceramic coating) just to be safe, and you're golden.
I think its just hard to find a dealer/body shop who actually knows how to properly respray SRCM or MGM. If you try to respray it like a typical paint, it won't come out well. I've heard of some shops getting a PPG rep to show them how to paint SRCM and MGM, and the repairs are supposed to be quite good.
I've had to get some significant paint repairs done to my MGM paint, and it came out looking brand new. That said, I think SRCM is harder to paint than MGM, and I have yet to see anyone post the results of an SRCM repaint (good or bad).