Hmm! Interesting.
The grape-skins are much thicker in korean & japanese grapes, and can be easily torn off by pinching. They are very unlike the American grapes, where the skin is basically extremely thin and stuck to the fruit. "I'm Korean and can confirm. Asian grapes are nothing like the grapes you'd get here in the United States."
Typically, you just pinch it and the insides just pop out and you toss the peels.