True, in Michigan it is a misdemeanor and requires force or coercion to be charged with criminal behavior. One could still be charged with jail time or a fine, but I imagine judges use jail time for those cases that involve mental impairment or alcohol or drug incapacitation, under age children etc. without any kind of penetration.
So technically if someone goosed you as you walked the quad you could technically maybe charge the person, but I can’t imagine a policing or justice system wasting time and taxpayer dollars on a groping charge. And if you were walking and the person who goosed you was walking the addition of having to prove force or coercion would be very difficult. I could see the police giving the person a stern lecture and I think this is the perfect case where a college could do some of that ed-u-ma-ca-tion. That same person who was goosed might have been terribly offended and answer in the affirmative if ever asked on a survey if they were assaulted (because they might associate being goosed with the word assault in their mind.)