Blizzard can put in hotfixes at any point that could cause a ban wave to happen.. so doesn't explain why a small patch takes 24 hours to change the id, again.
Those hotfixes is what tripwire is for I assume. They could just change the id and let everyone risk their accounts, but they don't want to do that because there is a high chance a bunch of people stop using their program if a massive banwave occurs.