I can’t remember. Did the AFL introduce the nomination rule because they thought your point about midfielders impeding ruckman was an issue?
Yeah, it came in when the third man up was banned so they would know who the two ruckman were and see that no other player got in their path to the ball.
The problem before were that teams without good ruckman (like Hawthorn) were going third man up every time to negate the opposition. It would have driven the pure ruckman types like Natanui, Gawn etc out of the game.