Simply put....
IR this season is simply a designation for an injured player. A player put on it is removed from the 53 man roster for a minimum of 3 games. That player could miss the entire season, 3 games or anything in between.
Coaches, GM's, media, fans, etc. stating "season ending injury and on IR" are just stating that the player suffered an injury that more than likely won't allow the player to play again. However, if a miracle occurs and the player is able to play, as long as he has been out for 3 games, he is still eligible to be put back on the 53, no matter what someone used for reasons why he was placed on IR.
The only "season ending" IR designations came back in August and Sept., before the final 53 man roster was announced. THOSE players seasons were officially over, even if a miracle of God occurred and their 2 broken legs were healed overnight.
The article OS posted is simply saying that a player can't return fron IR a second time. So if MVS goes on IR, he is done for the season and yes, you could call that "season ending IR"