Has ND changed their "we don't redshirt policy"?
It's my understanding that ND doesn't redshirt that is holding out players out of play in a given year to promote better balance on the team roster. Rather ND restricts some freshman from play based on size, development, and academics.
The NCAA allows athletes 5 years to play 4 years. However ND expects students to graduate in 4 years so a student athlete held out of play as a freshman may only get 3 years of PT at ND. A 4th year of PT can be made available as a Graduate Student known as 5th Years. Potential 5th Years have to be in qualified academic standing (degree, GPA, prerequisites, and faculty recommended) and must be offered a football scholarship.
I recall ND upperclassmen be held out a season for injury or surgery, such as Joe Montana, but don't recall an upperclassman be held out of play to balance the depth chart. As Romeo played as a freshman holding him out as a Sophomore to bulk up for another position and smooth out the depth chart would be within NCAA rules but would be a significant change in ND policy.