Personally I agree with you (actually I started fixing the rest of the tramways adding embedded_rails=tram, at least they'll be uniform).
The difference that was raised is that usually "tram" has 2 rails on which the tram rolls the wheels, while the Venice tram has just one rail and common rubber wheels for actually moving. To catch the peculiarity, probably we should use embedded_rails=monorail, but at this point I think we'll discuss in the forum - thanks for checking, though!