Since 1990 the true Freshman that have won NCAA titles are Pat Smith (mid weight), Teyon Ware (low/mid), Dustin Schlatter (mid weight, Kyle Dake (lower/mid), J'Den Cox (upper weight) and Myles Martin (mid/upper weight), Spencer Lee (lower weight), Mark Hall (mid), Yianni (mid), AJ Ferrari (upper).
I may have missed someone but as you can see the true freshman national champions are pretty evenly dispersed from lower to upper weights.