Yes Iowa finally switched to the 4-2-5 in 2018, at least when playing passing teams. Amani Hooker played the 5th DB position that Iowa likes to call the "cash" position. Hooker ended up winning Big Ten DB of the year in 2018.
It's not just a coincidence that after some fine-tuning the Iowa defense went almost 3 straight years from late 2018 to mid-2021 without giving up more than 24 points.