That's an interesting news but I don't think it will be Apple. Car manufacturing requires volume to be efficient (like any mass produced product, ça va sans dire). But it is also extremely expensive to ship compare to their retail price (you could put approximately two car in a full size container but 44k iPhones, do the math). Let's try to do the Apple's strategy. Apple could go for the Luxury market (BMW series 7, Maseratis and upper). The price, and more important, the margin you have, is high enough to make the transportation cost low enough. At the same time you don't have enough volume to have multiple factory. In this situation you build just one factory. Atlanta is an interesting spot due to it's good connections with the rest of the US and it's comparatively low labor cost (to the Bay Area). But it is on the east coast while it is probable an Apple Car in this price range will have more buyer on the West Coast. Plus in car manufacturing labor cost is a small factor (especially in the luxury segment). But staying close to the hq is a very important factor, especially for your first model. Plus, if you are planning to source component from Asia (electric motors, chips, batteries) being close to a port like LA or San Francisco could be a benefit.

Let's make the hypothesis that Apple is going for a relatively mass market instead (affordable premium, a BMW series 3, but the reasoning holds also for cheap subcompact). Apple probably needs more than one production plant if it plans to launch internationally, but a single plant is enough for the US market and the reasoning before still holds. Actually, in this scenario Apple needs to work out faster the productions issue so being closer to home is beneficial.

This obviously is true if you think Apple will produce the car. But it doesn't make sense based on their production philosophy, and it will be a massive investment when there are "white label" car manufacture ready to be the Foxconn of Apple Car. The first name I could came up is Magna Steyr but if they go for low volume super luxury there are a bunch of small manufacturer in Italy with a good pedigree (Touring, Bertone) with the know how, the production capacity, and the brand that fits Apple needs.

I'm not saying you are wrong, even if my bet for the plant in Atlanta is for a European Automaker, I'm just saying that looking at the logistics, building a plant in Atlanta is not really effective for Apple. Probably tax breaks could change this balance, but I doubt you could have secrecy and tax breaks for a business of this size.

Do you have a source to this?

I haven't seen any news regarding this in any of the auto websites or related sub-reddits