No, these are folds in the glass. Finding a seam on a swirl can be tough and often times the seam, which is more commonly called a cut on swirls, is folded and inside the marble. They are much smaller on swirls, by nature of the way they are made. On non-swirls, think of a fat stream of glass getting cut into blobs, little tootsie rolls of glass that get rolled into spheres. You can see the places where that gob of glass was cut from the stream and those are the seams. On a swirl, think of a longer squirt of toothpaste rolled into a sphere. Where the ends are can be hard to find and might have gotten rolled up on the inside or just smeared out and unrecognizable.