I presume this NNS topic information from the IC GitHub is outdated. As it doesn’t seem to have all the NNS topics anymore.
For topic 0 the code comments are as follows:
// The Unspecified topic is used as a fallback when
// following. That is, if no followees are specified for a given
// topic, the followees for this topic are used instead.
I’m wondering is this still true? On the NNS UI I am guessing that the “All except Governance, and SNS & Neurons’ Fund” is topic 0?