Although the Packers may want insurance of having someone behind center if AR and then Hundley go down, but if that happens (AR goes down), I doubt it would matter who is behind center, season over.
I think this was more along the lines of the Packers really liking Callahan and wanting back for the future.
Oh, they
had to sign a QB. If Callahan is the best available option in a 2016 emergency situation because he knows the system, so be it. If Tolzien were on the street instead of playing as Luck's backup, they might have signed his sorry a*s instead.
"Season over" may the overriding concern of a fan. I can assure you that the organization would still want to put its best foot forward in trying to win games.
If we assume Rodgers plays against Houston, entering a game with 2 QBs on the game day roster, albeit one being dinged up, is hardly a sin.
Let's say Rodgers' condition worsens and he can't play against Seattle.
Having 1 QB on the game day roster is extremely risky because if that guy goes down you're in the embarrassing situation of having to use Nelson or Cobb or whoever is the emergency QB. Besides Callahan, street QB options who don't know the system are unattractive. And if you waited until after the Houston game to sign Callahan, somebody might sign him ahead of you, perhaps a team that has the Packers coming up on the schedule.
Having only 2 QBs on the roster is risky to begin with. Having 1 dinged and 1 healthy is very risky. Having only one QB who can play is an embarrassing and a display of organizational incompetence. So, yeah, there are important concerns after "season over".