I think with that pattern that when you bind off, it will automatically make a scalloped edge. The pattern should tell you which row you need to complete before you start the bind off.
Sorry…I just looked at the pattern again and I see it doesn’t tell you the row to complete before binding off. But, my original answer still stands. I believe with a scalloped pattern like that it will naturally have the scalloped bound-off edge.
Yes, this has been my experience with scalloped patterns. The top edge only looks straight now because the needles hold it that way. Once it’s bound off it’ll be wavy. Do the BO on row 2 or row 3 of the pattern.