"The Sixth Circuit ... held that a dispute between a union and an employer regarding retiree healthcare benefits was not arbitrable because the issue of retiree healthcare benefits was not encompassed within the collective bargaining agreement's (CBA's) grievance procedures." [United Steel, Paper and Forestry, Rubber, Manufacturing, Energy, Allied Industrial and Service Workers International Union, AFL-CIO-CLC v. LLFlex, LLC, No. 19-5464 (6th Cir. Mar. 24, 2021)]