I think A/B testing may have value in selecting a specific path preferred by 85% of users, but it seems like alienating the remaining 15% doesn't feel great.

95% of users might not want the double-textbox, but 5% might, and some might want to use it someday.

I think, make enough of these decisions, and there's bound to be mounting friction for users with different preferences navigating your app.

Ideally, the app should offer a way for the user to intuitively configure the app to their own liking.