In another interview I heard him say that some drafts will have more of one type of player than others, but that you won't have a draft where there are little to no players of a certain archetype. In 18 there would be drafts where there were literally zero 3-4 tackling LBs available, or two blocking TEs.
In real life teams can pick a a college player who is totally off the radar of the other teams, because they feel like he is a perfect fit for what they want to do. Since the game is limited to something like 450 players in every draft, IMO it is fine that they manipulate the player types to allow for a fair number of every archetype because the game has probably less than 20% of the actual number of players that teams could draw from.