For me, if I am behind the plate, It would need to be obvious for me to call that. If it is a 50/50 ball though on the edge of the zone, Im calling it a strike 100% of the time, not on the checked swing but on the pitch. They need to be swinging. Base umpires have the better angle on checked swings. When i am working bases, A is the best to be picky. I look at the angle of the bat, if it comes past perpendicular to the line, he went. B and C it’s tough cause the angle, so unless even his mother knew he went, im not calling it.