His average of 16.3 is skewed by him sitting out most of the Southern Utah game when it was well in hand
Against FBS competition he's averaged 17.9 carries per game. If you include catches, he's been averaging 21 touches per game in that time. 2021 Tyler Allgeier (the definition of a workhorse back) averaged 23.4 touches per game.
So Bernard has been carrying more workload than you'd think at first. And he's certainly shown he can carry a large amount in a given game. He had 25 carries for 182 yards against Oklahoma St, and 21 for 129 (plus 5 catches for 61 yards more) against Arizona St
I think the bigger issue with his workload is that it's been much HIGHER than in past years. His last two games have been the two (aside from the SUU blowout) with the fewest carries and also been the two he's been least effective
Looking at the data, it's inarguable that he CAN be a workhorse back for a single game or two ... but I don't think he can keep it up over the course of a season and wears down when used that way