It firing on Scarif would be pretty weird. But then again that’s the sort of crazy thing that the Empire might do.
I thought when they destroy Alderaan in SW that it was the first time the superlaser was used.
Well, the RO trailer does show the DS firing on Jedha. However the super laser is most likely not fully operational at this point, hence it doesn’t blow up the entire planet and instead just causes a lot of destruction. I guess they did this in RO so that the DS can still be a big threat to the main characters without undermining ANH. Alderaan was simply the first test of the “fully operational” DS and its planet destroying capabilities. In RO it seem to only be capable of blowing up a city-sized area.