I don't think it matters if it is a 2 or 4 or 6 week injury in this case.
They can't use PUP, because it was not a preseason injury.
They won't use short term IR, because you use that for really good starting players and you only get one of those.
They are using IR, because they don't want to cut another 53 man roster player to add Long, again for an injured backup player.
We are acting like Bass is some beast we can not do without, he is a nice backup who might have some upside (hence putting him on IR) that has been on IR twice in the last 2 years.