Now you've got me wondering if there's any non-concord grape jelly to be had. I intend to inspect the shelves at my local grocery co-op in minute detail on my next trip! (The candy corn was a bust there by the way.)With the grapes it actually is a legit thing though. Concord grapes are a hybrid with a different species (vitis labrusca, the "fox grape," provides about 2/3 of its genes, with the remaining 1/3 mostly coming from the more typical species, vitis vinifera, the species usually used for table grapes and winemaking.) Methyl anthranilate is found in far higher concentrations in labrusca grapes.
Being perfectly honest, I had previously thought that Concord grape jelly was laced with artificial sources of methyl anthranilate in order to make it taste more like grape candy (in one of those "reality is unrealistic" kinds of ways.) So at least anecdotally, yes, there is a very distinctive difference between Concord grape flavor and "regular" grape flavors. (I personally prefer green or white grapes myself.) Coupled with the general social apprehension that "grape flavor doesn't taste like grapes, it just tastes 'purple',” I think we can reasonably conclude that there is a perceptual difference between the two and artificial flavoring sharpens that difference a lot.