So I’m curious about if this stuff will affect modern automotive paints.
Here is some of my experience with phosphoric acid ( and muriatic) which I believe may be close to your inquiry.
Never done car paint but have done all types of industrial coating and I imagine the effects are similar.
Naval jelly doesn't chemically destroy and or remove paint like muriatic acid ( except latex types or coats on improperly prepared surfaces) but it does get in the pores and makes it soft or otherwise changes properties in some ways ( you can visibly see the changes)
We use it for prep ( it etches very well) but has to have residue cleaned then a protective coating PDQ.
I have noticed ( based on surface finish of the substrate) that on a smooth prepped surface it softens paint but it still mostly sticks ( except if there is a crack then it makes it peel)- that said the remaining exposed paint clearly no longer has the qualities of the original so t has been 'affected' in some way and I would recommend removing it.
I have also seen on rougher castings where it doesn't seem to soak in the cracks and damage the paint at all.
I would ask someone in auto body for specifics, surely they would know