Sometimes you have nodes that overlap each other, so you want to control whether or not a node is in front of or behind another node.
Though yes, they could have explicitly defined a z-index or defined a convention on how the ordering should work (first nodes top and last nodes bottom or vice versa?). It's interesting to think about the trade offs between explicitly defining these things vs. leaving the application to implicitly make the choice. JSON Canvas seems to be designed to use in tandem with markdown files in a note taking app, so it makes sense why they opted for the more implicit design to be similar to markdown
Though yes, they could have explicitly defined a z-index or defined a convention on how the ordering should work (first nodes top and last nodes bottom or vice versa?). It's interesting to think about the trade offs between explicitly defining these things vs. leaving the application to implicitly make the choice. JSON Canvas seems to be designed to use in tandem with markdown files in a note taking app, so it makes sense why they opted for the more implicit design to be similar to markdown