I feel like they're just hitting the limits of a bash+shims based approach. I understand why they've done it, but in the end an implementation in a compiled language will beat that approach most of the time. There are issues since a shell hook will only work as long as you're, well, using a (supported) shell.

However, it's surprising to hear that they've been focusing on UX. The fact that you have to manually install a plugin, then install a version, and then finally set it, without the tool suggesting any of those steps to you when you forgot one, really makes the tool annoying to use when switching versions a lot.