[museav]

Those actually look a lot more like delayed fills than they do stage monitors. In that case, there's no inherently obvious reason for them being upside down, but it may be to get better HF (the horn pattern falls apart below around 1,500Hz) coverage of specific audience areas or to try to compensate for having limited down angle adjustment. If they work well with them upside down, then there's no reason to do differently, but there may also not be much real logic behind their being mounted upside down beyond simply that was how it was done.