Hey Dirk! Yes the rules do say the ball needs to be thrown up “near vertically” so there is always a bit of room there for slight differences. A lot of the top players do this, of course some more extreme than others, but a lot of them tread a fine line with serves and probably Par included, but they are still legal.
Again it will always come down to individual interpretation from each umpire and you have to be careful to not go to extreme with the throw angle.
Hope that makes sense, Regards, Tom
