I feel like I should point out that pure lead is really soft. So soft in fact that you should be able to easily scratch and deform it with a dull knife. Lead will also tarnish really quickly when heated and turn a flat grey color. Because of its low melting point, lead would also be a really bad filler metal for cast iron cookware. It would soften and fall out if you ever overheated the pan.
Try scratching a line through both the pan and the brighter area with the tip of a fork or a dull knife. If it's lead, the shiny area will scratch much deeper and feel different compared to the cast iron.
Also, filling a hole or a void with lead might be easy, but welding with steel is also easy and probably cheaper from a manufacturing perspective.
I am far from being an expert, but I would think the shiny spot is indeed a repair but with arc welded steel or an iron/nickel alloy. Both of which will be durable, stand up to heat beautifully, and also appear noticably shinier than cast iron even after being heated on the stove.
I'm starting to feel like violence is the answer to this kind of argument. I'm not there yet. But I get closer every time I see this shit.