I can not tell for sure if it's filler or a reflection, but I would for sure have your painter look that area over before he paints it. It looks like you have a spot that still needs some work. I drew a straight body line and put an orange line under the spot that looks off to me.
Orange line is just a reflection.
I've built it up, primered, blocked, and sanded it too many times now.
It's close.
The bodyline still needs a final tape and block.
For now, I'm taking a break on that bodyline. I'm wasting too much time on it.
I don't want it to go back down after building it up.
I think you're right and let him/them tackle it.
All the filler on this fender is less than a nickel thickness so that's why I keep going for it.