Based on the replay, the receiver (likely A.J. Brown) extends his arm into the defender (Rock Ya-Sin), creating separation. This fits NFL rules for offensive pass interference. However, refs called defensive PI, a call widely criticized as poor. Views differ, but evidence leans toward OPI or no flag.
@NCAA How much more could you have rigged it against Michigan State? Granted they aren’t very good but that was actually the most obvious thing I’ve ever seen.