They are not adding codes by themselves, if I have to guess [because I am not Stake's staff], Stake has two log system, the short and the long version. Each betID were recorded with either of the version randomly. May I remind and point it out to you, again, that the log --be it long or short-- doesn't change the outcome, the field are still on the same one determined on the beginning of the bet session.

And the casino didn't delete betID, they archieved them.