Okay, I know I'm showing my age with this post but here goes. When I was a teen, someone gave me some quilt templates. I was instructed to trace the template onto the fabric and then cut an ample seam allowance. There wasn't an exact amount like we use today. I tried doing as I was instructed but didn't like it and didn't make any quilts. I was a sewer...... 5/8" seams for clothing. So, when I started to try quilting again, I thought 1/4" was insane. Wouldn't the seam pull out??? Silly me.... the quilt is stitched together with batting and backing. No way could the seam pull out unless you mistakenly didn't catch in the edge.
Quilting has come a long way..... a really long way. I actually started quilting back around 1995 although I did do a baby quilt for my youngest son in 1976 ..... the old method. I now have tons of gizmos to do quilting.... my DH says that if they make it for quilting, I have it..... not true!!
Why would someone write a book using 1/2" seams?? Who knows. I'd just follow the patterns in that book with 1/2" and do the normal thing, 1/4", for other quilts. Problem solved!!