@archersf, @j.rosen, your experience sounds like mine. I created a wish list item because the behavior is very consistent when both my wife and I arrive home at the same time. See Cancel auto-unlock if bluetooth connects within 30 seconds of a prior auto-unlock event.
There are times when I haven’t noticed it auto-unlock after our arrival because I wasn’t watching. In those cases, I’ve inspected the lock history and have seen that it auto-locked after 10 minutes. Some kind of rule that kicks in because the door wasn’t opened within 10 minutes of the auto-unlock.