I believe this is pretty common simply due to the fact that teams want to hire their staff as soon as possible. If the Packers go the Super Bowl and win, most teams will have their important positions filled and any coaches looking for promotions will be out of luck. Several teams are doing this I believe, including the offensive coordinator of the Falcons, Panthers, etc. I don't think it's a huge distraction, but not ideal either. McCarthy will have this offense grooving either way.
Edit: Also, teams have to receive permission from the Packers to speak with their staff as well. No one would be leaving their job until the season is over either. It's just an interview. Perhaps they could get the job but they would still be expected to finish the season with their current team. I don't see it being much different than looking for another job while you're still at the current one, with the exception of your employer knowing about it 😉