Thanks Vitor for checking🙏
I think it's because the NIP10 deprecated version says this:
Two "e" tags: ["e",
I think most clients have interpreted this as the second/final "e" tag is the event being replied to, irrespective of root, but not Amethyst. Sharing a snort screenshot of this reply for your reference.

I only wish I could've raised a PR instead of bothering you but it looked like that would take months 😔