I've always thought of mind maps as spatially confused trees, and Org already does trees very well. This package introduces the "friends" concept -- is that the fundamental difference between trees and mind maps?
* Read Books
-- Book Title
Review
-- Author Name
-- Author Name 2
* Artists
-- Artist Name
But in org-brain I can connect all of these in a logical way so I can jump through it quickly.
You're right in that some of the data structure behind mind maps can be represented using a tree. However, you'd lose lots of the benefits. For example, trees might not be as memorable or as unique as a mind map[1].
[1]https://imindmap.com/blog/mind-mapping-for-memory-why-is-it-...