I haven't seen any sashiko fabric - just the quilting. I am guessing that it is printed to look like it is sashiko quilted and I think that would be lovely. I am sure it would make a beautiful quilt but it would need a pattern that doesn't cut up the fabric too much. I am thinking that you would also not want the pieces too big, as I think you would want to stitch in the ditch to quilt. If you did FMQ or a pattern over the fabric you wouldn't get the full effect. I am betting it would make a wonderful bag, jacket, etc.
I did some searching and didn't really see too much on the internet- in fact your store was one of the few that came up. The fabrics do look lovely