Yep agree.
Suspect that you have not seen this before as you do not have a worm problem.
A wormer will kill any worms present. These will include some that you won't see, but the long ones in the gut if present will come out. Typically they look like spagetti. They come out BECAUSE they are dead, so stop hanging onto the inside of the gut, so no chance that a worm will be alive. They shed eggs in the dung of the pig to multiply, they don;t come out live to find another host.
A wormer is not a preventative, it simply kills any infectation present.
So that is what you saw, which is telling you that you were right to worm them, so rather than panic give yourself a good pat on the back.