Hmm... history would suggest otherwise. Good for a career of low mileage NFL use like say, Darren Sproles... but even bringing him up he was an absolute beast statistically at Kansas State. Don’t get me wrong Johnson’s production is good and his elusiveness is
. That being said he’s on a team that is hesitant to give Kerryon Johnson more than 50% of the snaps. I have zero qualms with declaring emphatically he is not a feature back and would bet against him sustaining over 15 touches regularly given his use on a bad, bad Maryland team.
I think low mileage would be good in a vacuum, but the reason why it might not be correlated with NFL success/longevity is because the best players are going to tend to command a high workload in college, so the guys who come into the league with low mileage usually have low talent as well. A lot of the obvious exceptions are guys whose college depth charts were clogged ala Kamara, Drake, Gore, etc.
Maryland's other RB last year, Anthony McFarland Jr, had 1034 rushing yards at 7.9 YPC (!), so he's not exactly a slouch. I think he's a draftable prospect. I've compared him to Alex Collins, although looking at the height/weight, he may be more like a Tevin Coleman type. I don't think he's an elite talent, but he's a good enough player where losing touches to him isn't something to be hugely ashamed of.
I have Ty stashed on a lot of teams and I don't expect anything from him, but he had a high YPC in college with a high rate of explosive plays. He may not have gotten the ball a lot, but when he did, he made a lot of positive plays. As for him being a "featured back", that discussion may be largely beside the point. Austin Ekeler will never be a featured back, but look at the production he is putting up right now. Anyone who gets fed touches will score FF points, and in PPR leagues, the smaller combo backs can actually be more valuable than the two down thumpers who ostensibly have more ideal height/weight.
For what people paid for Ty Johnson (nothing), any outcome beyond pointless roster clogger is pure profit.