[umanwizard]

> Since the reliance is on convention, and an inverted rook is conventionally treated as a promoted queen

I think that convention is much less strong than the conventional meaning of the piece shapes. I have only seen it in casual games, and I’m not sure if it exists in every country.

I don’t know why this rule was adopted, but I gave a few plausible reasons off the top of my head in another post on this thread.