it's only one quilt- the top-raggy side and the back-
and no my seams do not come apart- i stitch each construction seam twice- and pay attention when clipping to not snip through any seams- if i do happen to snip a seam i go straight back to the machine and fix it
the edges will fray a bit more when washed a couple more times but then it will (be done) and not go any further- and it will not go past the joining/construction seams.
i have a raggy quilt i made 9 years ago-been washed many many times- has held up just fine.