frequently the selvedge is woven differently, tighter, than body of fabric & thus, shrinks unevenly from body of yardage. in vintage fabrics i have, the selvedge is so narrow it's barely 1/4" or less wide. i have one piece that selvedge so narrow that the fabric maker info printed about an inch from the edge ..a treasure i'll prob never cut up
..but all that said, i always prewash with color catchers, sort by color and trim off the selvedge before i start cutting my patches. in some vintage precuts or patches, like a bow tie quilt i'm currently working on that i got from an estate sale comprised of feed sack & vintage dress fabrics, they included the selvedge. i snip at intervals to reduce chance of puckering after being washed and dried. yes this works ...i have been sewing with vintage & antique fabrics from estate sales/auctions for 30 years.