That's exactly why this keyed supplemental lock was developed. It's an option for those that have your same concerns. It is an exclusive feature that you won't find anywhere else. The lock also provides a back up entry if desired (it can be disabled by the owner). If you watch this from a computer, there are annotations.
I will say though, that in almost 8 years I have never personally seen someone crack the code that way. Most of my experience has been with customers that somehow messed up trying to reset the combination.