The right mental model is to realise the 'main' branch is only special by convention - git doesn't actually treat it differently from any other branch.
All of the confusion expressed in the article stems from a misunderstanding that main should work in some special way.
Of course every branch's history goes all the way back to root and not to some arbitrary common commit of another branch like 'main'. Of course rebase and merge can work "backwards" from main onto some branch (because it's not "backwards" because main is not special - it just isn't done much in practice because keeping main straight helps with collaboration)
Furthermore, by realising that main isn't inherently special, it becomes obvious that the actions can be done between any two branches as needed.
The right mental model is - it's just commits, all the way down.
All of the confusion expressed in the article stems from a misunderstanding that main should work in some special way.
Of course every branch's history goes all the way back to root and not to some arbitrary common commit of another branch like 'main'. Of course rebase and merge can work "backwards" from main onto some branch (because it's not "backwards" because main is not special - it just isn't done much in practice because keeping main straight helps with collaboration)
Furthermore, by realising that main isn't inherently special, it becomes obvious that the actions can be done between any two branches as needed.
The right mental model is - it's just commits, all the way down.