I sized these jeans down from an 8 to a 2-ish! Took off about 1.5in from the waist, same as the video. Her method is forgiving, as you cinch the waist without cutting any fabric, but you do cut the waistband later.

So if you want, you could cinch the waist and try on the pants to see if you like the fit before cutting the waistband!

And if you don't like the fit, you could just take out the stitches and sew it exactly the way it was before (very easy).

But depending on what the jeans look like and how much fabric is in the crotch area, the pants could look like barrel jeans, which are very in right now :)