Check out this recent article on ESPN on how they are handling games and player statuses. Number 4 on the list is the latest update on when a player can be thrown into an IR spot for the week (besides if a player is specifically on the COVID list). This now gives us the ability to use the IR SLOT for when a game is postponed for the week and is not being replaced with their bye.
REMEMBER: If a player is on the IR or listed OUT for other reasons than having COVID or game postponements due to COVID, you cannot add them to your IR SLOTS!!