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.

Doesn't lead have a low melting point?

The main issue with lead contamination in cast iron cookware is that people sometimes use it to melt lead for things like making bullets and fishing weights.

So in most cases griddles are probably pretty safe, they have a very shallow if any rim, so they're not exactly ideal for holding a puddle of molten metal and pouring it into a mold. I'd be more concerned with pots and skillet that could hold liquid a little better.

That's not to say there's no risk though, I could certainly imagine someone using a griddle as a convenient heat-resistant surface to pour out leftover lead to cool on afterwards, but that's probably significantly less common.

If it's properly seasoned do you really need to worry about the lead? Your food would never come in contact.