This is the language I was referencing "However, at least with mutual funds, the funds could and often were managed in a substantively different manner. While large diversified mutual funds often have a big chunk of overlap, there are clearly at least some differences in the underlying stocks, as well as the manner by which the manager buys and sells those stocks over time. Given these differences, and what at least was usually just “limited” overlap, mutual funds have kept their “ordinarily not substantially identical” treatment." He then goes on to say that switching from one ETF to an identical ETF at a different provider probably won't pass muster.