Maybe - it doesn't specify in the directions. There is a selvedge stitch on the edges that is supposed to be exposed on the right side of the work. Here are the entire directions:
Sew Side pieces (with the reverse stockinette stitch side facing out)
to Front and Back pieces (with stockinette stitch side facing out) using mattress stitch and single-stitch seam allowance so that the seams are expressed (visible) on the RS of garment.
Sew shoulder seams. Sew sleeve seams using mattress stitch or backstitch and a single-stitch seam allowance. Set sleeves into armholes in the same manner.