Boy based off tubercle?!?!

I had first trimester testing yesterday. I measured 12 weeks 4 days even though I should be 11weeks 4days. Anyways the tech made a guess on gender based off some scientific method behind a tubercle  pointing up or down. I have no idea what she's talking about but she guesses it's a boy. She said don't buy anything blue yet though. Has anyone heard of this and is it accurate?