just now, i finally thought to look it up. Aztlan.net had the following to say:

“We Mexicans love our “tacos al carbon” and have never heard of “tacos del carbon”. We hope that Del Taco Corporation does not intend to sell us tacos with pieces of coal in them. “Tacos al carbon” refers to the fact the beef is grilled over hot coals. The “al” in “tacos al carbon” means the same as the often used French term “a la” which means ‘in the manner of’ or ‘in the style of’. Del Taco in using “Tacos del Carbon” is actually saying “tacos made of carbon”.

So in a way, that kid was right. And why SHOULDN’T carbon be present in your taco? Technically carbon should be present in every single ingredient found in a taco. Wikipedia calls carbon “the chemical basis of all known life”… which sort of explains the powerful lust i feel for tacos in MY life.

But yeah the nomenclature is still wrong here.