It's a fair complaint, but amethyst already has an issue with typing over the selected word rather than cursor location (at least for me), I'd be worried about layering spellcheck over the top of that. I've gotten so used to the graphene spellcheck that I don't think about it, but you are right, that is a UI issue that would annoy most users.
Pixel 7 pro
Only complaint with the device itself is that once in a while it's hard to reach all the way across the phone when doing things one handed 😅
OS is great, but for security reasons it's important to stick with the stock keyboard. Emoji selection is weak & autocorrect is buggy & unusable IMO. Not a problem in Telegram and many apps or websites that have their own emojis & spellcheck. Would love for Amethyst to add a basic spellcheck nostr:npub1gcxzte5zlkncx26j68ez60fzkvtkm9e0vrwdcvsjakxf9mu9qewqlfnj5z