Because it depends when those GCDs occur as some of those hardcasts happen under buff alignment, others in filler. All these things must be taken into account instead of trying to wash it off as inconsequential. It's one aspect of many and alignment really, really does matter for a job like Summoner with peaks and troughs where we build the rotations to take advantage of time windows as best as possible unlike jobs where buff alignment matters less because the general rotation plateaus better and hits more like a truck.