"[T]he government cites at least two plausible claims for breach of ERISA's duty of prudence ... They noted that the Seventh Circuit had determined that because the plaintiffs had access to some low-cost investment options, they could not object to the fiduciaries' decision to offer other investment vehicles that allegedly carried unreasonably high management or recordkeeping fees -- a position inconsistent with that of the Eighth Circuit -- and apparently with that of the [DOL]." [Hughes v. Northwestern Univ., No. 18-2569 (7th Cir. Mar. 25, 2020; cert. pet. filed Jun. 19, 2020; brief for U.S. as amicus curiae filed May 25, 2021)]