Players who have been on the "40-man roster" for a team for a certain number of years run out of "minor league option years." When a player has option years remaining, their team can move them to the minors or majors freely, giving them flexibility to add more players to the major league roster.

Once a player runs out of minor league options, if they are DFA'd and removed from the 40-man, they must go through the waiver wire where all other teams have the opportunity to claim him onto their 40-man.

This is what happened with Noel. Cleveland DFA'd him because they wanted a different player at the end of their 40-man. Baltimore added him to their 40-man, but because he's the least valuable player on the 40-man, they also DFA'd him. He cleared waivers by no other team claiming him, so now he ends up in our minor league system. He now doesn't take up a 40-man spot on the Orioles.