It looks like some of the pre-wound bobbins are the 'M' size--used in LA's..... probably polyester thread. Great find and great savings!
The pre-wounds don't need to be put on your bobbin. Just slide into bobbin case and thread like normal. Some of the machines need to have both side of the cardboard taken off to work right. No, it doesn't hurt the bobbin or the way your machine will work because these are packed so tight they won't fall apart.