no its not! haha it has nothing to do with spinning ON the rail
pretezel is a 270 off going the opposite motion of which you got on...
snowboarders say frontboard pretzel, crook pretzels, etc...
skiers just rail slide pretzel or 270 on pretzel, etc...
so if you grind left foot first, then if you 270 out spinning left, then it would be a pretzel ( as it would oppose the motion you got on)