I am fairly certain the only transaction that falls under the 'moves' category is adds (FA or waivers).
Is this legal just because the system allows it? If it was not legitimate the system wouldn't allow it basically, and it is within the confines and parameters of the game.
In the past the system would not have allowed this, if a player was on the DL and was activated during the trade processing period the trade would simply disappear on the day it was supposed to process and you'd have most of the managers in the league wondering what just happened.
This newer system, while i do feel it is still slightly flawed, is the better of the 2 options.