How Valuable is a "Generational Running Back"

Bijan Robinson is considered a "Generational Running Back" according to most draft scouts and seems to be the surest thing in the draft, but why has he not come up that much in mock drafts?Unbearable Merch Store: https://www.unbearablesports.shop/Transparent Labs https://tinyurl.com/53tfj9mxBet.US use promo code UNBEARABLE to get 125% in bonuses https://bit.ly/UnbearableBetUS