We're on the same page, haha. Our discussion of different ways to cut the mechanics also gave me the thought that it'd be amusing to have a "UFO 50" style framing for different game modes. :p
But yeah, it all does rest on the premise that hinged trominoes would somehow have been more practical or natural than conventional tetrominoes. Thought experiments like this just reinforce what we already knew about the functional/mechanical benefit of tetrominoes. Alternative piece sets can be made to work, but will often have some sort of rough edges (e.g., this game's "T"). If it seems to us as a more challenging variant of the genre we're already familiar with, then how plausible is it that this would have been conceived of as the "path of least resistance" for our hypothetical alt-timeline designers?