Those are machine-made cutlines, not pontils. The marble-making machinery has shears. The shears cut off the globs of molten glass which become the marbles. That gives a cutline on the top and the bottom of the marble.
Or if the glass is more of a stream than a glob like your last marble, it will result in a swirl. There will still be two cuts on a swirl. But sometimes the cut marks will get wrapped up inside the marble so you can't always see it. But with your first two marbles, we have a nice, clear top and bottom.