They are worried about bugs, but they address those in other ways. This is some of the most extensively integration tested software there is (I was part of the team that built the integration testing). Every commit is ran through a custom CI system that successively tests pieces of the system working together up to and including automated hardware tests. The number of lines of code dedicated to testing the vehicle is definitely much greater than the lines of code on the vehicle.
I'm aware of that; I commented because I'm surprised by it.
I'm sure the issue was discussed so I'm not implying that they are idiots. But it does seem odd to me.