It looks like one of the arguments raised by plaintiffs is that the policy violates Indiana's anti-vaccine-passport law, HB 1405 (see page 10 of the full text), which was just signed into law in late April 2021. Obviously previous precedent would not have taken this law into account, and it is possible that IU's policy, even if it had been upheld as legal under previous law, may be in violation of this new law. The courts will have to decide anew.
Part of the controversy is that the new law only forbids "the state or a local unit" from requiring "immunization passports". According to https://wgntv.com/news/what-does-indianas-new-vaccine-passport-law-do/, part of IU's argument is that they are neither the state nor a local unit, that such wording is generally understood in Indiana law to not include public universities, and that the legislature deliberately chose that wording in order to exclude public universities.