Hey guys, just to clear out any doubts.
Related positions are mostly used when you don't have a player for certain positions for the formation you wanna play. So with this you can put every player (except) GK on two more positions, but your team will be slight penalized for that - it's not like it was before where you get huge penalty for having players on the wrong positions, instead you have very small penalty. Huge penalty is given when you place player on any positions besides his native and related positions. The penalty for wrong positions is bigger as you go further away from player's native position, and also increases with the number of players on wrong positions.

If player has two roles he will have more than two related positions.

Hope this clears it
Cheers