The difference last year vs prior redshirt guys is they had weeks where they really had no RB depth and they basically decided to run Rhamondre into the ground. Look especially at the games where Damien Harris was unavailable (and keep in mind, Ty Montgomery got hurt in Week 1):
Week 6 vs Cleveland: Rhamondre a whopping 60 snaps, KHarris 12, Strong 4
Week 9 vs Indy: Rhamondre 46 snaps, KHarris still inactive, Strong 0 snaps, JJ Taylor up from PS 17 snaps
Week 13 vs Buffalo: Rhamondre 53 snaps, KHarris 1 snap, Strong 0 snaps
then Rhamondre also got hurt against Arizona (just 13 snaps) so you actually had some snaps for the kids: 29 KHarris, 19 Strong
Week 15 vs LV: Rhamondre 43 snaps, KHarris 7, Strong 13
Week 16 Cincy: Rhamondre 51, KHarris 4, Strong 2
There were snaps to be had last year with the injuries they had in that group; it was a lot different situation than, say, Damien Harris' rookie year (when they had a still-well-regarded Sony plus Burkhead, White, and Bolden). But they just rode Stevenson harder. I haven't checked but I expect he played the most snaps any single RB has in Belichick's tenure.