These creases can be from adherent scar tissue forming bands or sutures under the skin pulling that area towards the ear. If there are permanent sutures, those would need to be cut. If there are scar tissue bands then undermining like your plastic surgeon is recommending should work. Four months post op is a reasonable time period. Your healing is complete and you should recover quick.
The most important thing is NOT to remove any fat as usually the fat covers up any irregularities and keeps the skin looking smooth. If for some reason that does happen down the road, you might need a filler to smoothen out the wrinkles.
Regards



