[lolinder]

This doesn't quite answer the question, because you could say the same thing about UI code:

If you have your state distributed in an OOP-style GUI, the "am I checked" state of the checkbox should always correspond to the boolean value in the model, if it doesn't then something went wrong.

The point of SSOT is that you don't want to architect code such that there has to be more code designed to keep things in sync, because there's the possibility that that syncing code goes wrong. Distributed databases aren't exempt from that, we just have a high level of trust that the people who wrote the syncing code know what they're doing.