I've seen that same thing on brand new AC lines before. I'd say it's factory. When rolled in mfg, the inner diameter bend increases in thickness and the outer one thins out. Bending such lines always "weakens" the outer area of the bend....even if just be thinning the outer wall diameter. But it still has to meet min wall specs. I inspected 800 psi boiler tubes for years....and saw the same thinning on tubes up to 1/4 inch thick.
I'd use it. Now if that really is a non-mfg dent from post production damage/impact, it took a lot of force to do that in such isolation. It should have put a heavy stress on the fitting/welds that goes into the condenser/tank. The tube bend directly above the one you mention also seems to have some flattening on the outer roll.