The ordinary wholecut is a leather upper, cut and stitched into the typical conical shape required of an upper before lasting and then pulled over the last. A cool style because it is a single piece of leather, very dressy and a great way to show off the shape of the last.
The seamless wholecut is a further refinement of the technique. Rather than disturbing the leather upper with a seam, it is lasted as-is with no cutting and rejoining, so essentially a flat piece of leather. This is a much more delicate procedure and requires a much longer period of time to complete. Haste in this case would certainly make waste. The leather upper is under lot more stress during the lasting phase and it could easily tear.
That’s me in the mornings