I'm hearing that the PPF might not have UV protection, but the ceramic coating does. In that case, the paint could possibly age differently and cause a slight change in color when comparing the two areas? Not sure, even if true, it would be something that could be noticed and be a real problem. I'm guessing not.I'm still wondering why a ceramic coat is desirable on top of a self-healing PPF. Here's my thoughts:
When heated in even just outdoor sunlight self-healing PPF will heal over light scratches and swirls and restore itself to a smooth surface. I can confirm this worked well with the SunTech Ultra PPF I used. The dealership that sold it to me for my Porsche had a test you could do. They had a small sample piece of painted "hood" and a brass brush. You could use the brush to visibly scratch the PPF. Once scratched, they had an IR heat lamp to heat the surface. With your own eyes you could watch the PPF heal itself back to a nice gloss in around 30 seconds or so.
So then why do you need to add scratch-resistant ceramic coat on top of that? It just seems like an unnecessary extra expense. I've used both and like both in their place, both help prevent minor scratches and swirls and both make bug splat removal much easier. I have full-body ceramic coat on the I-Pace and it seems to do well. But it certainly doesn't protect against chips from small gravel like PPF does, yet full body PPF is very expensive. It was just shy of $5k on the Porsche. So a reasonable approach in my mind is to use the expensive PPF in forward facing chip-prone areas and more cost-effective ceramic coating everywhere else... but again... I don't see the need to use ceramic on top of the PPF since it can just take care of it's own scratch resistance and healing.
By the way, with bigger deeper hits even PPF will take damage that does not heal, but it will usually protect the paint underneath it from chipping. Then it can be removed and replaced by the piece if the damage is enough to bother you.
Here's a YouTube video of someone demoing the self-healing of the XPel PPF equivalent of the Suntek Ultra I used... it's pretty amazing:
I also just read that the car's original clearcoat should have UV protection, which would minimize or eliminate this concern.