I agree that memory perspective is probably at least partly linked to physical brain architecture and chemistry at the time the memory is formed, and when its recalled. I’ve actually read one study that third-person memory could be partly linked to depression, so that’s interesting. Another study says that third-person memories are likely to be older memories.
Here’s an interesting article I found about memory perspective. https://www.psychologytoday.com/blog/mental-mishaps/201309/the-directors-cut-point-view-in-memory