The specific ergonomics of rowing dictate the shape and function of the garments. In the 1980`s when I did my short stint as a rower, rowing kit design was far different from the designs of today. There has been a massive transformation of rowing kit design due to the incredible developments of stretch fabrics used in so many different sports. These new fabrics allow far more freedom of movement.
The rowing uni-suit, used for both training and racing is designed for function and comfort. The shape is similar to the tri-suit, or the cyclists all-in-one suit, with many similar properties. Because the uni-suit needs to be put on over the head, without a zip, the neck opening has to be large enough to do this easily and without breaking the stitching. Both the fabric and the stitching need to be stretchy enough to allow for this. The leg opening needs to be tight enough so that it doesnt creep up the leg while rowing. Some elastic may be added to help this. And the back leg needs to incorporate a half lining that adds some extra protection from wear and chafing. This is usually stitched on to the outer fabric with a zig-zag stitch.