That's interesting, I didn't know that before, so I did a bit of research on this, and while you are right that Cacao seeds do absorb some lead naturally when growing, a couple studies have shown that most of the lead that ends up in cacao likely comes from after the farming stage,

Because of the high capacity of cocoa bean shells to adsorb lead, contamination from leaded gasoline emissions may occur during the fermentation and sun-drying of unshelled beans at cocoa farms. ... However, the much higher lead concentrations and larger variability in lead isotopic composition of finished cocoa products, which falls within the global range of industrial lead aerosols, indicate that most contamination occurs during shipping and/or processing of the cocoa beans and the manufacture of cocoa and chocolate products. source

So most lead contamination came from processing the chocolate rather than from the tree absorbing it. Also, the same article says that the lead is likely from gasoline vapors, not from the soil,

One source of contamination of the finished products is tentatively attributed to atmospheric emissions of leaded gasoline, which is still being used in Nigeria. Because of the high capacity of cocoa bean shells to adsorb lead, contamination from leaded gasoline emissions may occur during the fermentation and sun-drying of unshelled beans at cocoa farms. Source (same as before)

I haven't read the whole article, but I think this is good enough to serve as a counter-argument. Also, I know the article says "cocoa" instead of "cacao", but it seems "cocoa" is basically just processed "cacao", according to this article on healthline. So basically, the use of cacao and cocoa is inconsistent and may just refer to cocoa beans and/or processed cocoa beans.

Also, I found this article, which seems like the abstract to this source, but I can't figure out if it really is or not. If anyone has any idea of the relationship between the two articles I'd be happy to hear it.