I'll see if I can find it, but it doesn't change the fact that I can identify the varietals in many wines. Yes there is some gray area. An oaked Sauvignon Blanc may taste a lot like an oaked Chardonnay and may be hard to differentiate.
Even a Merlot with 25% Cabernet and a Cabernet with 25% Merlot may be hard to pick, but a good Pinot Noir and a good Cabernet. No contest.
Andy